tests: always send 'quit' to stop the VSM
tests: always send 'quit' to stop the VSM

Always send 'quit' at the end of the input to cleanly shut down the
VSM process.  This is especially needed as the main loop doesn't stop
when an IPC module returns None any more.

Signed-off-by: Guillaume Tucker <e7e20b7c30f19d4ca6b81319ef81bf200369d137@collabora.com>

GENIVI/vehicle_signal_manager