MediaProvider: get UUID of removable volumes for non-FAT filesystems

Change-Id: I0a66d6c169f3da8fb69af09e543d56df2d84e347
Make sure date taken time is set

computeTakenTime() depends on the value DATE_MODIFED,
so call it after DATE_MODIFIED are set to ensure it
works correctly.

Change-Id: Ib4f3b03c487b45dd081dab5bd4ddfa72221b434f