Make rssi state change sticky

NetworkController misses the rssi state at boot. It gets the wifi
connection status because it is sticky. The rssi state will remain
out of sync until the wifi state machine sends another update which may
not happen if rssi does not change significantly.

Make rssi sticky as well to make sure NetworkController has the last known
signal strength on wifi.

Bug: 6916156
Change-Id: Id7dd621c6dbc35d7354757c61aa18a3b1ba90593