### 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': [],
            'collections': [],
        }
        b_requirements_file = to_bytes(requirements_file, errors='surrogate_or_strict')
        if not os.path.exists(b_requirements_file):
            raise AnsibleError("The requirements file '%s' does not exist." % to_native(requirements_file))
        display.vvv("Reading requirement file at '%s'" % requirements_file)
        with open(b_requirements_file, 'rb') as req_obj:
            try:
                file_requirements = yaml_load(req_obj)
            except YAMLError as err:
                raise AnsibleError(
                    "Failed to parse the requirements yml at '%s' with the following error:\n%s"
                    % (to_native(requirements_file), to_native(err)))
        if file_requirements is None:
            raise AnsibleError("No requirements found in file '%s'" % to_native(requirements_file))
        def parse_role_req(requirement):
            if "include" not in requirement:
                role = RoleRequirement.role_yaml_parse(requirement)
                display.vvv("found role %s in yaml file" % to_text(role))
                if "name" not in role and "src" not in role:
                    raise AnsibleError("Must specify name or src for role")
                return [GalaxyRole(self.galaxy, self.lazy_role_api, **role)]
            else:
                b_include_path = to_bytes(requirement["include"], errors="surrogate_or_strict")
                if not os.path.isfile(b_include_path):
                    raise AnsibleError("Failed to find include requirements file '%s' in '%s'"
                                       % (to_native(b_include_path), to_native(requirements_file)))
                with open(b_include_path, 'rb') as f_include:
                    try: