Remove /data/misc/vold/user_keys/ce/${user_id} when no longer needed

When a user is removed, vold is deleting the subdirectories of
/data/misc/vold/user_keys/ce/${user_id} but not that directory itself.
This is unexpected, as none of the user's directories should be left
around.  Delete it too.

Bug: 188702840
Test: pm create-user foo
      pm remove-user 10
      stat /data/misc/vold/user_keys/ce/10 # no longer exists
Change-Id: Id4033a668fa6de1debb9ba6fdd1351c940bd35fc
1 file changed