Keyguard: Fix configuration change observer

Change I9e5dfdb12df522dc7dd50c26f35aba26b1bbe44e made recreations
only happen when a stored copy of the previous configuration differs
from the current one. But "configuration = otherConfiguration" creates
a reference to the original object, not a copy, so newConfig.diff(mLastConfiguration)
always returned zero. Fixit by creating an actual deep copy of the
Configuration object.

Change-Id: I236932dfc0e121dd83212882b4fe71306c8a3fab