setup-alpine: do not restart networking service when run headless

Setting-up Alpine on Headless system requires network interfaces are not restarted if modified during the process.
Recent change 39c91c14 unconditionally forced networking restart.
We add a condition to restart unless under active SSH connection (i.e. when running headless).

Fixes #10503 (closed)

note: ssh client install later-on in script does not cause trouble: start command will gracefully fail issuing a warning message, which is expected in such headless situation.