##### SUMMARY
The documentation mentions the ability to specify a galaxy server parameter via the syntax `ANSIBLE_GALAXY_SERVER_{{ id }}_{{ key }}`, but this seems to not be working for the URL of an example of this.

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
lib/ansible/cli/galaxy.py

##### ANSIBLE VERSION
```
ansible --version
ansible 2.9.0.dev0
  config file = None
  configured module search path = ['/Users/alancoding/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /Users/alancoding/Documents/repos/ansible/lib/ansible
  executable location = /Users/alancoding/.virtualenvs/ansible3/bin/ansible
  python version = 3.6.5 (default, Apr 25 2018, 14:23:58) [GCC 4.2.1 Compatible Apple LLVM 9.1.0 (clang-902.0.39.1)]
```

##### CONFIGURATION
```
ANSIBLE_NOCOWS(env: ANSIBLE_NOCOWS) = True
```

##### OS / ENVIRONMENT
Mac OS, control machine, also on CentOS


##### STEPS TO REPRODUCE
Run this command

```yaml
ANSIBLE_GALAXY_SERVER_GALAXY_URL=https://galaxy.ansible.com ANSIBLE_GALAXY_SERVER_PRIVATE_GALAXY_URL=https://galaxy-dev.ansible.com ANSIBLE_GALAXY_SERVER_LIST=private_galaxy,galaxy ansible-galaxy collection install -r fallback_not_found/collections/requirements.yml -p dest -vvvv
```

where the content is

```
cat fallback_not_found/collections/requirements.yml
collections:
  - name: "chrismeyersfsu.test_things"
  - name: "chrismeyersfsu.tower_modules"
```

##### EXPECTED RESULTS
I expect it to attempt to install from the development galaxy server, and then get a 404, and then install from the release galaxy server.

This works if I do not use these environment variables and instead use the config:

```
[galaxy]
server_list = dev_galaxy,galaxy

[galaxy_server.dev_galaxy]
url=https://galaxy-dev.ansible.com

[galaxy_server.galaxy]
url=https://galaxy.ansible.com/
```

The documentation describes this use case here:

https://github.com/jborean93/ansible/blob/devel/docs/docsite/rst/dev_guide/collections_tech_preview.rst

> As well as being defined in the ansible.cfg file, these server options can be defined as an environment variable. The environment variable is in the form ANSIBLE_GALAXY_SERVER_{{ id }}_{{ key }} where {{ id }} is the upper case form of the server identifier and {{ key }} is the key to define. For example I can define token for release_galaxy by setting ANSIBLE_GALAXY_SERVER_RELEASE_GALAXY_TOKEN=secret_token.

The setting for the host is `url`

> url: The URL of the galaxy instance to connect to, this is required.

##### ACTUAL RESULTS
```
ansible-galaxy 2.9.0.dev0
  config file = None
  configured module search path = ['/Users/alancoding/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /Users/alancoding/Documents/repos/ansible/lib/ansible
  executable location = /Users/alancoding/.virtualenvs/ansible3/bin/ansible-galaxy
  python version = 3.6.5 (default, Apr 25 2018, 14:23:58) [GCC 4.2.1 Compatible Apple LLVM 9.1.0 (clang-902.0.39.1)]
No config file found; using defaults
ERROR! No setting was provided for required configuration plugin_type: galaxy_server plugin: private_galaxy setting: url 
```

I also tried removing "galaxy" from the names, and this has the same result.

```
ANSIBLE_GALAXY_SERVER_FOO_URL=https://galaxy.ansible.com ANSIBLE_GALAXY_SERVER_BAR_URL=https://galaxy-dev.ansible.com ANSIBLE_GALAXY_SERVER_LIST=bar,foo ansible-galaxy collection install -r fallback_not_found/collections/requirements.yml -p dest -vvvv
ansible-galaxy 2.9.0.dev0
  config file = None
  configured module search path = ['/Users/alancoding/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /Users/alancoding/Documents/repos/ansible/lib/ansible
  executable location = /Users/alancoding/.virtualenvs/ansible3/bin/ansible-galaxy
  python version = 3.6.5 (default, Apr 25 2018, 14:23:58) [GCC 4.2.1 Compatible Apple LLVM 9.1.0 (clang-902.0.39.1)]
No config file found; using defaults
ERROR! No setting was provided for required configuration plugin_type: galaxy_server plugin: bar setting: url 
```

Ping @jborean93 @chrismeyersfsu @ryanpetrello 

We do _not_ rate this as a Tower blocker, because the `ansible.cfg` specification of parameters is known to work, and we will begin to design around that.
in_templates_dir = rel_root_dir == 'templates'
            dirs[:] = [d for d in dirs if not any(r.match(d) for r in skeleton_ignore_re)]
            for f in files:
                filename, ext = os.path.splitext(f)
                if any(r.match(os.path.join(rel_root, f)) for r in skeleton_ignore_re):
                    continue
                elif galaxy_type == 'collection' and own_skeleton and rel_root == '.' and f == 'galaxy.yml.j2':
                    
                    
                    
                    
                    template_data = inject_data.copy()
                    template_data['name'] = template_data.pop('collection_name')
                    meta_value = GalaxyCLI._get_skeleton_galaxy_yml(os.path.join(root, rel_root, f), template_data)
                    b_dest_file = to_bytes(os.path.join(obj_path, rel_root, filename), errors='surrogate_or_strict')
                    with open(b_dest_file, 'wb') as galaxy_obj:
                        galaxy_obj.write(to_bytes(meta_value, errors='surrogate_or_strict'))
                elif ext == ".j2" and not in_templates_dir:
                    src_template = os.path.join(rel_root, f)
                    dest_file = os.path.join(obj_path, rel_root, filename)
                    template_env.get_template(src_template).stream(inject_data).dump(dest_file, encoding='utf-8')
                else:
                    f_rel_path = os.path.relpath(os.path.join(root, f), obj_skeleton)
                    shutil.copyfile(os.path.join(root, f), os.path.join(obj_path, f_rel_path))
            for d in dirs:
                b_dir_path = to_bytes(os.path.join(obj_path, rel_root, d), errors='surrogate_or_strict')
                if not os.path.exists(b_dir_path):
                    os.makedirs(b_dir_path)
        display.display("- %s %s was created successfully" % (galaxy_type.title(), obj_name))
    def execute_info(self):