Missing an await on dns.write_hosts call

[mdegat01]

Proposed change

Missing an await in a call to plugin_dns.write_hosts

23-07-31 16:40:27 DEBUG (MainThread) [supervisor.homeassistant.websocket] Queuing message until startup has completed: {'type': <WSType.SUPERVISOR_EVENT: 'supervisor/event'>, 'data': {'event': <WSEve
/usr/src/supervisor/supervisor/addons/__init__.py:462: RuntimeWarning: coroutine 'PluginDns.write_hosts' was never awaited
  self.sys_plugins.dns.write_hosts()
RuntimeWarning: Enable tracemalloc to get the object allocation traceback

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New feature (which adds functionality to the supervisor)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue:
• Link to documentation pull request:
• Link to cli pull request:

Checklist

• The code change is tested and works locally.
• Local tests pass. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the development checklist
• The code has been formatted using Black (black --fast supervisor tests)
• Tests have been added to verify that the new code works.

If API endpoints of add-on configuration are added/changed:

• Documentation added/updated for developers.home-assistant.io