### Summary

`ansible-galaxy collection install` makes a lot of requests to galaxy.ansible.com and can occasionally hit the rate limit. When that happens, galaxy.ansible.com will return a 520 http code and `ansible-galaxy` fails to download the collection and exits. Ideally when the client encounters a rate limiting http code (either 520, or 429), it should wait, slow down the request rate and try again rather than exiting.

More information is available here: https://github.com/ansible/galaxy/issues/2429 

### Issue Type

Bug Report

### Component Name

ansible-galaxy

### Ansible Version

```console
$ ansible --version
root@ubuntu-s-1vcpu-1gb-nyc3-01:~# ansible --version
ansible 2.10.7
  config file = None
  configured module search path = ['/root/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/local/lib/python3.8/dist-packages/ansible
  executable location = /usr/local/bin/ansible
  python version = 3.8.5 (default, Jan 27 2021, 15:41:15) [GCC 9.3.0]
```


### Configuration

```console
$ ansible-config dump --only-changed
root@ubuntu-s-1vcpu-1gb-nyc3-01:~# ansible-config dump --only-changed
root@ubuntu-s-1vcpu-1gb-nyc3-01:~#
```


### OS / Environment

All

### Steps to Reproduce

Run `ansible-galaxy collection install `amazon.aws`. If your internet is fast enough, this will occasionally fail when galaxy.ansible.com returns a 520 error code.

### Expected Results

Collection should be installed.

### Actual Results

```console
`ansible-galaxy` encounters a 429 or 520 http code and exits.
```


### Code of Conduct

I agree to follow the Ansible Code of Conduct


"""
        Gets the collection information from the Galaxy server about a specific Collection version.
        :param namespace: The collection namespace.
        :param name: The collection name.
        :param version: Version of the collection to get the information for.
        :return: CollectionVersionMetadata about the collection at the version requested.
        """
        api_path = self.available_api_versions.get('v3', self.available_api_versions.get('v2'))
        url_paths = [self.api_server, api_path, 'collections', namespace, name, 'versions', version, '/']
        n_collection_url = _urljoin(*url_paths)
        error_context_msg = 'Error when getting collection version metadata for %s.%s:%s from %s (%s)' \
                            % (namespace, name, version, self.name, self.api_server)
        data = self._call_galaxy(n_collection_url, error_context_msg=error_context_msg, cache=True)
        self._set_cache()
        return CollectionVersionMetadata(data['namespace']['name'], data['collection']['name'], data['version'],
                                         data['download_url'], data['artifact']['sha256'],
                                         data['metadata']['dependencies'])
    @g_connect(['v2', 'v3'])
    def get_collection_versions(self, namespace, name):
        """
        Gets a list of available versions for a collection on a Galaxy server.
        :param namespace: The collection namespace.
        :param name: The collection name.
        :return: A list of versions that are available.
        """
        relative_link = False