SystemUi: init controllers once

Change-Id: I6f1317d4267c8455a7dcde2ae0c828163884b506
Change SQL to improve performance.

To know the number of images, use "COUNT(*)" instead of "_id" in SQL.
Using "_id" gets all result set. and when getCount() is called, CursorWindow is filled.
But using "COUNT(*)" gets just 1by1 data.
So using "COUNT(*)" is more faster than now.
And this SQL is called everytime per a file during a file transfer in MTP
The better way is by using "EXIST".
But if using "EXIST", modify MediaProvider.call() method.
So i applied just a "COUNT(*)"

Change-Id: Ic5882af0fad2304f836b7b7043a4746359391609
Signed-off-by: muzbit.kim <muzbit.kim@lge.com>
Prevent a duplicated registration of Observers

If same Observer and same URI are registered, the callback functions are called multiple times
when data identified by a given content URI changes.
It makes system slow and it cause ANR sometimes.
And When run unregisterContentObserver(), just one deleted
but others are remained in mObservers.
So add prevent code to avoid to duplicated registraion of Observers

Change-Id: I5c7845deb682db289ff0d53150ef012174859767
Signed-off-by: muzbit.kim <muzbit.kim@lge.com>