Fix batterystats update on sensor connection cleanup

Previous code was stopping battery tracking for *all* sensors activated
by the UID, rather than only the sensors activated in the
SensorEventConnection being cleaned up, leading to under-counting of
sensor activation time.

Fixes: 210559152
Test: verify batterystats correctly updates when one connection is
      closed and another remains open
Change-Id: Id6b96929c5534295334eeca3d56506d29bc75b29