### Summary

To reproduce, run these commands where `ns.col` is the name of a collection you do not have installed and the value of `-p` is a valid collection path that exists:

`ansible-galaxy collection list ns.col -p collections/`
`$?`

The output of $? on devel is 0, but since the collection wasn't found it should be 1. The same issue exists for listing specific roles that do not exist.

To fix:
1. [This method](https://github.com/ansible/ansible/blob/stable-2.14/lib/ansible/cli/galaxy.py#L1494-L1502) needs to return the correct exit code from `execute_list_role` and `execute_list_collection`.

2. `execute_list_collection` and `execute_list_role` will need to be fixed to return 1 if a collection/role was requested and not found.
For example, on [this line ](https://github.com/ansible/ansible/blob/stable-2.14/lib/ansible/cli/galaxy.py#L1680) add
```python
        if not collection_found and collection_name:
            return 1
```

3. Add a new test to [this file](https://github.com/ansible/ansible/blob/stable-2.14/test/integration/targets/ansible-galaxy-collection/tasks/list.yml), similar to [this one](https://github.com/ansible/ansible/blob/stable-2.14/test/integration/targets/ansible-galaxy-collection/tasks/list.yml#L111-L116) that lists a single collection that does not exist. Then add an assert task following it to test that the command result's rc is 1.

4. Add a `bugfixes` [changelog fragment](https://docs.ansible.com/ansible/latest/community/development_process.html#creating-a-changelog-fragment).

### Issue Type

Bug Report

### Component Name

ansible-galaxy

### Ansible Version

```console
$ ansible --version
ansible [core 2.15.0.dev0]
```


### Configuration

```console
# if using a version older than ansible-core 2.12 you should omit the '-t all'
$ ansible-config dump --only-changed -t all
```


### OS / Environment

N/A

### Steps to Reproduce

<!--- Paste example playbooks or commands between quotes below -->
```bash (paste below)
ansible-galaxy collection list ns.col -p collections/
$?
```

### Expected Results

1

### Actual Results

```console
0
```


### Code of Conduct

- [X] I agree to follow the Ansible Code of Conduct
'required': required,
                'type': option_type,
            }
            if key in SERVER_ADDITIONAL:
                config_def.update(SERVER_ADDITIONAL[key])
            return config_def
        galaxy_options = {}
        for optional_key in ['clear_response_cache', 'no_cache', 'timeout']:
            if optional_key in context.CLIARGS:
                galaxy_options[optional_key] = context.CLIARGS[optional_key]
        config_servers = []
        
        server_list = [s for s in C.GALAXY_SERVER_LIST or [] if s]
        for server_priority, server_key in enumerate(server_list, start=1):
            
            
            
            config_dict = dict((k, server_config_def(server_key, k, req, ensure_type)) for k, req, ensure_type in SERVER_DEF)
            defs = AnsibleLoader(yaml_dump(config_dict)).get_single_data()
            C.config.initialize_plugin_configuration_definitions('galaxy_server', server_key, defs)
            
            server_options = C.config.get_plugin_options('galaxy_server', server_key)
            
            
            auth_url = server_options.pop('auth_url')
            client_id = server_options.pop('client_id')
            token_val = server_options['token'] or NoTokenSentinel
            username = server_options['username']
            v3 = server_options.pop('v3')
            validate_certs = server_options['validate_certs']