fs_mgr: Drop the context mount option from non-selinux builds

This will require that transitioning devices have context as the
last mount option, since everything after it will be ignored

Change-Id: Ic5cc7f5632cc3d62459dfaaf7719d662737e1641
Merge branch 'cm-10.1' of github.com:CyanogenMod/android_system_core into cm-10.1