### 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
"""
        Install one or more roles(``ansible-galaxy role install``), or one or more collections(``ansible-galaxy collection install``).
        You can pass in a list (roles or collections) or use the file
        option listed below (these are mutually exclusive). If you pass in a list, it
        can be a name (which will be downloaded via the galaxy API and github), or it can be a local tar archive file.
        :param artifacts_manager: Artifacts manager.
        """
        install_items = context.CLIARGS['args']
        requirements_file = context.CLIARGS['requirements']
        collection_path = None
        signatures = context.CLIARGS.get('signatures')
        if signatures is not None:
            signatures = list(signatures)
        if requirements_file:
            requirements_file = GalaxyCLI._resolve_path(requirements_file)
        two_type_warning = "The requirements file '%s' contains {0}s which will be ignored. To install these {0}s " \
                           "run 'ansible-galaxy {0} install -r' or to install both at the same time run " \
                           "'ansible-galaxy install -r' without a custom install path." % to_text(requirements_file)
        
        collection_requirements = []
        role_requirements = []
        if context.CLIARGS['type'] == 'collection':
            collection_path = GalaxyCLI._resolve_path(context.CLIARGS['collections_path'])
            requirements = self._require_one_of_collections_requirements(