Update Inet state when NetworkMonitor re-evaluates a network.

Previously the Inet state (the little exclamation mark beside the WiFi
and Cellular bars) only transitioned from bad to good once.  With this
change it can transition back to bad (and later to good again) if a network
re-evaluation is triggered, say by ConnectivityManager.reportBadNetwork.
Also, avoid triggering re-evaluation in two unwanted cases.

bug:16214361
Change-Id: I7856724249ffcbb0945276dcf45019876231fdaf