vold: allow non-vfat devices to be used as ASEC

CM supports alternative file systems (which some devices specify
in the fstab as 'auto').

Change-Id: I7e78fe87a7efc49d6749d5892107085d55156cce
vold: force SELinux context only for sdcard

It needs of https://gerrit.omnirom.org/#/c/2746/

Change-Id: I7b3db6a88ca9c2268f9176acdfc292335f8e25b3
Merge "vold: force SELinux context only for sdcard" into android-4.4