GatewayScanController: fix missing update of timestamp
GatewayScanController: fix missing update of timestamp

The timestamp of the last started scan was never updated.

Fixes: f2276357a401 ("GatewayScanController: restart scan if not in progress")
Signed-off-by: Jan Viktorin <3eab6ac54c005c4408f608556a6663b7f2abede7@fit.vutbr.cz>

BeeeOn/server,BeeeOn/server,BeeeOn/server,BeeeOn/server