System Bridge - Handle OSError for switched off devices

[timmo001]

Proposed change

Handle OSError as a connection error for System Bridge

Type of change

• Bugfix (non-breaking change which fixes an issue)

Additional information

• This PR fixes or closes issue: fixes System Bridge - OSError when WebSocket Disconnects #59311

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 homeassistant tests)
• Tests have been added to verify that the new code works.

If the code communicates with devices, web services, or third-party tools:

• The manifest file has all fields filled out correctly.
  Updated and included derived files by running: python3 -m script.hassfest.
• New or updated dependencies have been added to requirements_all.txt.
  Updated by running python3 -m script.gen_requirements_all.
• For the updated dependencies - a link to the changelog, or at minimum a diff between library versions is added to the PR description.
• Untested files have been added to .coveragerc.

The integration reached or maintains the following Integration Quality Scale:

• 🥈 Silver

To help with the load of incoming pull requests:

• I have reviewed two other open pull requests in this repository.