toolbox: Add levelFromUid categorization support to restorecon

This is necessary for the app data relabeling on migrated devices
to include the proper app context. Freshly installed apps get this
done automagically, as do newly created files.

Change-Id: If7421dac01c6ae8bd78e66f71e69298ed850a7ab
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
Fix building without SELINUX

since the scon is now a mandatory arg, it needs to exist even if
NULL

Change-Id: I8ba31a7a8cf357e9b0c43cee81ab49d3eb192819
Merge remote-tracking branch 'upstream/jb-mr1' into jb-mr1