<!--- Verify first that your issue is not already reported on GitHub -->
<!--- Also test if the latest release and devel branch are affected too -->
<!--- Complete *all* sections as described, this form is processed automatically -->

##### SUMMARY
<!--- Explain the problem briefly below -->
We publish semver collection (vyos.vyos:0.0.1-dev58) to ansible galaxy, however by default it seems ansible-galaxy client will not be able to find it. You must specific the version number directly to fetch it.

https://galaxy.ansible.com/vyos/vyos


EDIT:

This is working as expect, but it would be nice to Include:

   --pre                       Include pre-release and development versions. By default, ansible-galaxy only finds stable versions.

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
<!--- Write the short name of the module, plugin, task or feature below, use your best guess if unsure -->
ansible-galaxy

##### ANSIBLE VERSION
<!--- Paste verbatim output from "ansible --version" between quotes -->
```paste below
ansible 2.9.1
```

##### CONFIGURATION
<!--- Paste verbatim output from "ansible-config dump --only-changed" between quotes -->
```paste below

```


##### STEPS TO REPRODUCE
<!--- Describe exactly how to reproduce the problem, using a minimal test-case -->

<!--- Paste example playbooks or commands between quotes below -->
```yaml
$ ansible-galaxy collection install vyos.vyos -p /tmp/11123
[WARNING]: The specified collections path '/tmp/11123' is not part of the configured Ansible collections paths '/home/pabelanger/.ansible/collections:/usr/share/ansible/collections'. The
installed collection won't be picked up in an Ansible run.

Process install dependency map
ERROR! Cannot meet requirement * for dependency vyos.vyos from source 'https://galaxy.ansible.com/api/'. Available versions before last requirement added: 
Requirements from:
	base - 'vyos.vyos:*'
(venv) [pabelanger@localhost openstack]$ ansible-galaxy collection install vyos.vyos:0.0.1-dev57 -p /tmp/11123
[WARNING]: The specified collections path '/tmp/11123' is not part of the configured Ansible collections paths '/home/pabelanger/.ansible/collections:/usr/share/ansible/collections'. The
installed collection won't be picked up in an Ansible run.

Process install dependency map
Starting collection install process
Installing 'vyos.vyos:0.0.1-dev57' to '/tmp/11123/ansible_collections/vyos/vyos'
```

<!--- HINT: You can paste gist.github.com links for larger files -->

##### EXPECTED RESULTS
<!--- Describe what you expected to happen when running the steps above -->
vyos.vyos collection to be found and installed

##### ACTUAL RESULTS
<!--- Describe what actually happened. If possible run with extra verbosity (-vvvv) -->

<!--- Paste verbatim command output between quotes -->
```paste below

```

if not tarfile.is_tarfile(b_path):
            raise AnsibleError("Collection artifact at '%s' is not a valid tar file." % to_native(b_path))
        info = {}
        with tarfile.open(b_path, mode='r') as collection_tar:
            for b_member_name, property_name in CollectionRequirement._FILE_MAPPING:
                n_member_name = to_native(b_member_name)
                try:
                    member = collection_tar.getmember(n_member_name)
                except KeyError:
                    raise AnsibleError("Collection at '%s' does not contain the required file %s."
                                       % (to_native(b_path), n_member_name))
                with _tarfile_extract(collection_tar, member) as member_obj:
                    try:
                        info[property_name] = json.loads(to_text(member_obj.read(), errors='surrogate_or_strict'))
                    except ValueError:
                        raise AnsibleError("Collection tar file member %s does not contain a valid json string."
                                           % n_member_name)
        meta = info['manifest_file']['collection_info']
        files = info['files_file']['files']
        namespace = meta['namespace']
        name = meta['name']
        version = meta['version']
        meta = CollectionVersionMetadata(namespace, name, version, None, None, meta['dependencies'])
        return CollectionRequirement(namespace, name, b_path, None, [version], version, force, parent=parent,
                                     metadata=meta, files=files)
    @staticmethod
    def from_path(b_path, force, parent=None):