Fix Settings crash

Doesn't unregister contentprovider so that when data changed,
the fragment is destroyed.

Fixes: 127726564
Test: Connect to wifi. Go to Settings -> connected devices ->
      connection preference -> printing -> hp print service -> press
      back. Repeat several times.

Change-Id: I79d1522ce9d91a6bf6b1f982b7687eab1f7896bb