### 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
roles_path = opt_help.argparse.ArgumentParser(add_help=False)
        roles_path.add_argument('-p', '--roles-path', dest='roles_path', type=opt_help.unfrack_path(pathsep=True),
                                default=C.DEFAULT_ROLES_PATH, action=opt_help.PrependListAction,
                                help='The path to the directory containing your roles. The default is the first '
                                     'writable one configured via DEFAULT_ROLES_PATH: %s ' % default_roles_path)
        collections_path = opt_help.argparse.ArgumentParser(add_help=False)
        collections_path.add_argument('-p', '--collections-path', dest='collections_path', type=opt_help.unfrack_path(pathsep=True),
                                      default=AnsibleCollectionConfig.collection_paths,
                                      action=opt_help.PrependListAction,
                                      help="One or more directories to search for collections in addition "
                                      "to the default COLLECTIONS_PATHS. Separate multiple paths "
                                      "with '{0}'.".format(os.path.pathsep))
        cache_options = opt_help.argparse.ArgumentParser(add_help=False)
        cache_options.add_argument('--clear-response-cache', dest='clear_response_cache', action='store_true',
                                   default=False, help='Clear the existing server response cache.')
        cache_options.add_argument('--no-cache', dest='no_cache', action='store_true', default=False,
                                   help='Do not use the server response cache.')
        
        type_parser = self.parser.add_subparsers(metavar='TYPE', dest='type')
        type_parser.required = True
        
        collection = type_parser.add_parser('collection', help='Manage an Ansible Galaxy collection.')
        collection_parser = collection.add_subparsers(metavar='COLLECTION_ACTION', dest='action')
        collection_parser.required = True
        self.add_download_options(collection_parser, parents=[common, cache_options])
        self.add_init_options(collection_parser, parents=[common, force])
        self.add_build_options(collection_parser, parents=[common, force])
        self.add_publish_options(collection_parser, parents=[common])
        self.add_install_options(collection_parser, parents=[common, force, cache_options])
        self.add_list_options(collection_parser, parents=[common, collections_path])