ueventd: Add policy support for ueventd labeling changes

Currently, ueventd only modifies the SELinux label on a file
if the entry exists in /ueventd.rc. Add policy support to enable
an independent restorecon_recursive whenever a uevent message occurs.

Change-Id: I0ccb5395ec0be9282095b844a5022e8c0d8903ac