SystemUI: Avoid NPEs during status bar recreation for MSIM

PS2:
   * Clear the subs views on recreation
   * Unregister receivers on recreation

Change-Id: Id131ffac497f46a753a97b479823e51fda7c412c
Merge branch 'cm-11.0' of https://github.com/CyanogenMod/android_frameworks_base into android-4.4_new