### 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
return self.lazy_role_api.api
    def _get_default_collection_path(self):
        return C.COLLECTIONS_PATHS[0]
    def _parse_requirements_file(self, requirements_file, allow_old_format=True, artifacts_manager=None, validate_signature_options=True):
        """
        Parses an Ansible requirement.yml file and returns all the roles and/or collections defined in it. There are 2
        requirements file format:
            # v1 (roles only)
            - src: The source of the role, required if include is not set. Can be Galaxy role name, URL to a SCM repo or tarball.
              name: Downloads the role to the specified name, defaults to Galaxy name from Galaxy or name of repo if src is a URL.
              scm: If src is a URL, specify the SCM. Only git or hd are supported and defaults ot git.
              version: The version of the role to download. Can also be tag, commit, or branch name and defaults to master.
              include: Path to additional requirements.yml files.
            # v2 (roles and collections)
            ---
            roles:
            # Same as v1 format just under the roles key
            collections:
            - namespace.collection
            - name: namespace.collection
              version: version identifier, multiple identifiers are separated by ','
              source: the URL or a predefined source name that relates to C.GALAXY_SERVER_LIST
              type: git|file|url|galaxy
        :param requirements_file: The path to the requirements file.
        :param allow_old_format: Will fail if a v1 requirements file is found and this is set to False.
        :param artifacts_manager: Artifacts manager.
        :return: a dict containing roles and collections to found in the requirements file.
        """
        requirements = {