Fix crashes when clearing storage for a protected package

When clearing storage for a protected package,
ActivityManager throws a SecurityException.

This change catches the exception then shows a dialog
with the message "Couldn't clear storage for app".

Bug: 191806850
Test: manual visual
      1. Lock the device.
      2. Clear storage for a protected package.
Change-Id: Ic3e2c2237c6ee6dc945b03dac35b3b96a26129a9