Quicksettings: Avoid possible NPEs & improve controllers handling

Controller patch based on Clark Sheff's one: recreate controllers at start() only.
https://github.com/CyanogenMod/android_frameworks_base/commit/e95bc124c629cef485bb7ac4ce55137bf500f772

Shutdown all controllers and nullify quicksettings when recreating status bar
view at makeStatusBarView() before a controller and/or mQS instance is called.

Contributors:
@linuxman94
@BigBrother1984

Signed-off-by: Evan Anderson <evan@thelinuxman.us>
Signed-off-by: Carlo Savignano <stevewatersy@gmail.com>
Change-Id: I607dacf79f09fe208d481435cba8ca8c072758d6