Perform cleanup operation on destroy()

In some cases, it's possible that the destructor of the
SensorEventConnection object is never called, because unless
the cleanupConnection() call is made, the SensorService still
has a strong reference to the SensorEventConnection. This may
result in leaked resources, because the connection still exists
in the SensorService, though the connection has been destroyed
from the client's perspective.

This CL fixes this issue by doing the cleanup operation in the
destroy() call instead.

Bug: 274595196
Test: Run STS test, and verify all connections are destroyed afterwards

Change-Id: I7edb72d17337420e19352874bcae1d36b5981b95