Settings: fix media scan on boot behaviour

The settings reorganization patch forgot to move the actual java
code for this preference to the Memory class.

Add respective code and clean up old unused code.

Change-Id: Ic1b8251e45990514bb51a2ff07f5c9a12fae32bf
Merge "Settings: fix media scan on boot behaviour" into kk4.4-caf
Automatic translation import

Change-Id: Ice0a6ac0e4eaacdd4294f9eac88fba4de8b19482
Merge remote-tracking branch 'slimroms/kk4.4-caf' into kk4.4-caf