fs_mgr: add support for "sync" mount flag

Change-Id: I6ad74cfbf98d30320785e3691df30dabc5c54cb9
Remove HAVE_SELINUX guards

Android 4.3, and by extension CM 10.2, default to having SELinux on

Change-Id: Ie7853727102725a75a7d6fa3b3b35b1ffaacd89a

Conflicts:
	fs_mgr/Android.mk