[Provider Model] Fix preference summary not update.

 - When activity enter onPause, the status will not update, then
 sub id of TelephonyManager keep same value after activity go back.

 - Solution: Everytime update the UI, and always get new
 TelephonyManager with the latest sub id.

Bug: 181196545
Test: atest passed.
Test: Manual test passed.
Change-Id: I1d65bbc06af66b97b6c85f40bed394da03213d06