recovery: allow relabelto unlabeled and other unlabeled rules

The recovery script may ask to label a file with a label not
known to the currently loaded policy. Allow it.

Addresses the following denials:

  avc:  denied  { relabelto } for  pid=143 comm="update_binary" name="vdc" dev="mmcblk0p25" ino=212 scontext=u:r:recovery:s0 tcontext=u:object_r:unlabeled:s0 tclass=file
  avc:  denied  { setattr } for  pid=143 comm="update_binary" name="vdc" dev="mmcblk0p25" ino=212 scontext=u:r:recovery:s0 tcontext=u:object_r:unlabeled:s0 tclass=file

Change-Id: Iafcc7b0b3aaea5a272adb1264233978365648f94