Ringtone picker is not affected by current sonification policy

Add the FLAG_BYPASS_INTERRUPTION_POLICY AudioAttributes flag when
  launching the ringtone picker so it is not affected by the
  current sonification policy, in order to ensure the audibility
  of the phone ringtone or default notification being previewed
  by the user.

Bug 19407114

Change-Id: Ibd24e3f14e56e67f9e37576a84c97a73f5494074