##### SUMMARY
See https://app.shippable.com/github/ansible-collections/community.general/runs/6193/46/console for an example, I've already seen this multiple times today (also on AZP).

`ansible-galaxy -vvv collection install ansible.posix` was run three times in a row, and ~~always~~ two times out of three failed with `This collection only contains pre-releases.` (the first fail was a read timeout):

```
+ ansible-galaxy -vvv collection install ansible.posix
01:54 [DEPRECATION WARNING]: Ansible will require Python 3.8 or newer on the 
01:54 controller starting with Ansible 2.12. Current version: 2.7.15+ (default, Feb  
01:54 9 2019, 11:33:22) [GCC 5.4.0 20160609]. This feature will be removed from 
01:54 ansible-core in version 2.12. Deprecation warnings can be disabled by setting 
01:54 deprecation_warnings=False in ansible.cfg.
01:54 /root/venv/lib/python2.7/site-packages/ansible/parsing/vault/__init__.py:44: CryptographyDeprecationWarning: Python 2 is no longer supported by the Python core team. Support for it is now deprecated in cryptography, and will be removed in the next release.
01:54   from cryptography.exceptions import InvalidSignature
01:55 [WARNING]: You are running the development version of Ansible. You should only
01:55 run Ansible from "devel" if you are modifying the Ansible engine, or trying out
01:55 features under development. This is a rapidly changing source of code and can
01:55 become unstable at any point.
01:55 [DEPRECATION WARNING]: Setting verbosity before the arg sub command is 
01:55 deprecated, set the verbosity after the sub command. This feature will be 
01:55 removed from ansible-core in version 2.13. Deprecation warnings can be disabled
01:55  by setting deprecation_warnings=False in ansible.cfg.
01:55 ansible-galaxy 2.11.0.dev0
01:55   config file = None
01:55   configured module search path = [u'/root/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
01:55   ansible python module location = /root/venv/lib/python2.7/site-packages/ansible
01:55   ansible collection location = /root/.ansible
01:55   executable location = /root/venv/bin/ansible-galaxy
01:55   python version = 2.7.15+ (default, Feb  9 2019, 11:33:22) [GCC 5.4.0 20160609]
01:55   jinja version = 2.11.2
01:55   libyaml = True
01:55 No config file found; using defaults
01:55 Starting galaxy collection install process
01:55 Found installed collection ansible.netcommon:1.4.1 at '/root/.ansible/ansible_collections/ansible/netcommon'
01:55 Found installed collection community.kubernetes:1.1.1 at '/root/.ansible/ansible_collections/community/kubernetes'
01:55 Found installed collection community.internal_test_tools:0.2.1 at '/root/.ansible/ansible_collections/community/internal_test_tools'
01:55 Skipping '/root/.ansible/ansible_collections/community/general/.git' for collection build
01:55 Skipping '/root/.ansible/ansible_collections/community/general/galaxy.yml' for collection build
01:55 Found installed collection community.general:2.0.0 at '/root/.ansible/ansible_collections/community/general'
01:55 Found installed collection google.cloud:1.0.1 at '/root/.ansible/ansible_collections/google/cloud'
01:55 Process install dependency map
01:55 Processing requirement collection 'ansible.posix'
01:55 Opened /root/.ansible/galaxy_token
01:56 Collection 'ansible.posix' obtained from server default https://galaxy.ansible.com/api/
01:56 ERROR! Cannot meet requirement * for dependency ansible.posix from source 'https://galaxy.ansible.com/api/'. Available versions before last requirement added: 
01:56 Requirements from:
01:56 	base - 'ansible.posix:*'
01:56 This collection only contains pre-releases. Utilize `--pre` to install pre-releases, or explicitly provide the pre-release version.
```

It could be that for some reason, only the first page of the results is queried (https://galaxy.ansible.com/api/v2/collections/ansible/posix/versions/), which contains only pre-releases. I guess this is probably a problem on Galaxy's side, but in case it is not, I'm creating this issue in ansible/ansible.

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
ansible-galaxy collection

##### ANSIBLE VERSION
```paste below
devel
```

return self._available_api_versions
    def _call_galaxy(self, url, args=None, headers=None, method=None, auth_required=False, error_context_msg=None,
                     cache=False):
        url_info = urlparse(url)
        cache_id = get_cache_id(url)
        if cache and self._cache:
            server_cache = self._cache.setdefault(cache_id, {})
            iso_datetime_format = '%Y-%m-%dT%H:%M:%SZ'
            valid = False
            if url_info.path in server_cache:
                expires = datetime.datetime.strptime(server_cache[url_info.path]['expires'], iso_datetime_format)
                valid = datetime.datetime.utcnow() < expires
            if valid and not url_info.query:
                
                path_cache = server_cache[url_info.path]
                if path_cache.get('paginated'):
                    if '/v3/' in url_info.path:
                        res = {'links': {'next': None}}
                    else:
                        res = {'next': None}
                    
                    
                    res['results'] = []
                    for result in path_cache['results']: