### 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
display.display("WARNING: More than one Galaxy role associated with Github repo %s/%s." % (github_user, github_repo),
                                color='yellow')
                display.display("The following Galaxy roles are being updated:" + u'\n', color=C.COLOR_CHANGED)
                for t in task:
                    display.display('%s.%s' % (t['summary_fields']['role']['namespace'], t['summary_fields']['role']['name']), color=C.COLOR_CHANGED)
                display.display(u'\nTo properly namespace this role, remove each of the above and re-import %s/%s from scratch' % (github_user, github_repo),
                                color=C.COLOR_CHANGED)
                return 0
            
            display.display("Successfully submitted import request %d" % task[0]['id'])
            if not context.CLIARGS['wait']:
                display.display("Role name: %s" % task[0]['summary_fields']['role']['name'])
                display.display("Repo: %s/%s" % (task[0]['github_user'], task[0]['github_repo']))
        if context.CLIARGS['check_status'] or context.CLIARGS['wait']:
            
            msg_list = []
            finished = False
            while not finished:
                task = self.api.get_import_task(task_id=task[0]['id'])
                for msg in task[0]['summary_fields']['task_messages']:
                    if msg['id'] not in msg_list:
                        display.display(msg['message_text'], color=colors[msg['message_type']])
                        msg_list.append(msg['id'])
                if task[0]['state'] in ['SUCCESS', 'FAILED']:
                    finished = True
                else:
                    time.sleep(10)
        return 0
    def execute_setup(self):