Add check for UID reuse.

The goal here is to make sure that we aren't allocating a UID that
could have been in use since the last time the device booted.

Bug: 8256571

(cherry picked from commit af70d15543c89a53f064492f4e3d17c446e00039)

Change-Id: I8b11811df8d5a8ad1aa064abb43db020aceb29e3