After turning off the ethernet settings via api, the ethernet service can still be started when plugging-in the cable. Improve the api by ignoring the upcoming interface unsolicited event listener callbacks and register new interface observer once the ethernet setting is enabled again. Bug: 231933028 Test: atest testListenEthernetStateChange_unsolicitedEventListener Change-Id: I1b1cb7d157f023fca82d75592168bd360a6fa6e1