### Summary

The `hostname` module crashes with a `TypeError` exception when the file-based strategy is used (e.g. when handling a Devuan host).

### Issue Type

Bug Report

### Component Name

hostname

### Ansible Version

```console
$ ansible --version
ansible [core 2.12.2]
  config file = /home/tseeker/ansible/main/ansible.cfg
  configured module search path = ['/home/tseeker/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /home/tseeker/.virtualenvs/ansible/lib/python3.9/site-packages/ansible
  ansible collection location = /home/tseeker/.ansible/collections:/usr/share/ansible/collections
  executable location = /home/tseeker/.virtualenvs/ansible/bin/ansible
  python version = 3.9.2 (default, Feb 28 2021, 17:03:44) [GCC 10.2.1 20210110]
  jinja version = 3.0.3
  libyaml = True
```


### Configuration

```console
$ ansible-config dump --only-changed
DEFAULT_ASK_VAULT_PASS(/home/tseeker/ansible/main/ansible.cfg) = True
DEFAULT_HOST_LIST(/home/tseeker/ansible/main/ansible.cfg) = ['/home/tseeker/ansible/main/inventory']
DEFAULT_JINJA2_EXTENSIONS(/home/tseeker/ansible/main/ansible.cfg) = jinja2.ext.do
HOST_KEY_CHECKING(/home/tseeker/ansible/main/ansible.cfg) = False
USE_PERSISTENT_CONNECTIONS(/home/tseeker/ansible/main/ansible.cfg) = True
```


### OS / Environment

Devuan Chimaera on both the host running Ansible and the target.

### Steps to Reproduce

Tested with : 

```bash
ansible -m ansible.builtin.hostname -a 'name=target' target
```

Various values for `use` were attempted.

### Expected Results

I expected the `hostname` to do exactly nothing as it was already configured on the machine in question.

### Actual Results

```console
The plugin crashes with the following traceback :


Traceback (most recent call last):
  File "/home/administrator/.ansible/tmp/ansible-tmp-1644935764.4447377-23987-132310327618278/AnsiballZ_hostname.py", line 259, in <module>
    _ansiballz_main()
  File "/home/administrator/.ansible/tmp/ansible-tmp-1644935764.4447377-23987-132310327618278/AnsiballZ_hostname.py", line 246, in _ansiballz_main
    exitcode = debug(sys.argv[1], zipped_mod, ANSIBALLZ_PARAMS)
  File "/home/administrator/.ansible/tmp/ansible-tmp-1644935764.4447377-23987-132310327618278/AnsiballZ_hostname.py", line 213, in debug
    runpy.run_module(mod_name='ansible.modules.hostname', init_globals=None, run_name='__main__', alter_sys=True)
  File "/usr/lib/python3.9/runpy.py", line 210, in run_module
    return _run_module_code(code, init_globals, run_name, mod_spec)
  File "/usr/lib/python3.9/runpy.py", line 97, in _run_module_code
    _run_code(code, mod_globals, init_globals,
  File "/usr/lib/python3.9/runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File "/home/administrator/.ansible/tmp/ansible-tmp-1644935764.4447377-23987-132310327618278/debug_dir/ansible/modules/hostname.py", line 891, in <module>
    main()
  File "/home/administrator/.ansible/tmp/ansible-tmp-1644935764.4447377-23987-132310327618278/debug_dir/ansible/modules/hostname.py", line 885, in main
    'before': 'hostname = ' + name_before + '\n'}
TypeError: can only concatenate str (not "list") to str
```

This is caused by line 260 of `hostname.py`, which returns the array containing all the lines in whatever file `FileStrategy` is currently reading rather than just one line.


### Code of Conduct

- [X] I agree to follow the Ansible Code of Conduct
platform = 'FreeBSD'
    distribution = None
    strategy_class = FreeBSDStrategy
class NetBSDHostname(Hostname):
    platform = 'NetBSD'
    distribution = None
    strategy_class = FreeBSDStrategy
class NeonHostname(Hostname):
    platform = 'Linux'
    distribution = 'Neon'
    strategy_class = FileStrategy
class DarwinHostname(Hostname):
    platform = 'Darwin'
    distribution = None
    strategy_class = DarwinStrategy
class VoidLinuxHostname(Hostname):
    platform = 'Linux'
    distribution = 'Void'
    strategy_class = FileStrategy
class PopHostname(Hostname):
    platform = 'Linux'
    distribution = 'Pop'
    strategy_class = FileStrategy
class EurolinuxHostname(Hostname):
    platform = 'Linux'
    distribution = 'Eurolinux'
    strategy_class = RedHatStrategy
def main():
    module = AnsibleModule(
        argument_spec=dict(