We used to hash the file_context and skip the restorecon on the top
level directory if the hash doesn't change. But the file_context
might change after an OTA update; and some users experienced long
restorecon time as they have lots of files under directories like
/data/media.
This CL tries to hash all the partial match entries in the
file_context for each directory; and skips the restorecon if that
digest stays the same, regardless of the changes to the other parts
of file_context.
This is a version ported from Android that was originally written by:
xunchang <xunchang@google.com>
Signed-off-by: Richard Haines <richard_c_haines@btinternet.com>
