Launcher3: Do not react to Menu button when in 'All apps' mode

Avoid entering overview mode while in 'All apps' mode.

Change-Id: I39d006569f4f0d4f6eb521cdad4e475430337a3f
Merge branch 'cm-11.0' of git://github.com/CyanogenMod/android_packages_apps_Launcher3 into kitkat