Keyguard: smooth background change.

Change-Id: Ia0e4d0000db72b5cdb6fede03791805e34fa311d
Make "SD Card removed" notification dismissible if the removed SD Card is not the primary storage

The Galaxy S uses the "external SD Card" as the extended storage
and it the notification should be dismissible as it's okay not
to have it.

Additionally, this patch also not hide the USB storage mount dialog
if the removed storage is not the primary storage

Adapted for CM 11

Change-Id: Ic752a3da917e0d7736a619fb68f07905106987fb