conman: Avoid losing track of wpa_supplicant link.

Under circumstances not yet fully understood, conman may mistakenly
think wpa_supplicant is down and never discover the mistake, causing it
to remove routes for that interface.  This adds a regular check for the
link state to make sure this doesn't happen.

BUG=31261343

Change-Id: I3fe8cd905ef44f605d94952ef34685f1ca5fb862
2 files changed