Fix "No service" is not shown without SIM

"Emergency calls only" is shown instead of "No service" in statusbar
even if within the area specified by
"config_display_no_service_when_sim_unready" in the following cases.

1. Power on the device without SIM.
   When updateSpnDisplay() is called, the country code may not be
   updated yet. So the plmn keeps as "Emergency calls only".

2. Remove SIM card from the device which supports hot swap SIM.
   After removing the SIM, the UiccApplication becomes null.
   If UiccApplication is null, mIsSimReady is not updated to false.
   "No service" is not shown when mIsSimReady is true,
   so the problem occur.

How to fix the problem:
1. When last known country code is changed, update plmn by
   updateSpnDisplay().
2. If UiccApplication is null, update mIsSimReady to false.

Test: manual - "No service" is shown in lock screen and statusbar
without SIM.
Test: auto - Passed ServiceStateTrackerTest.
Bug: 151881495

Change-Id: I8115fdd0b4760069a309a55ddd8b579785d7ce46