Meter is not re-installed after OLT delete

Meter state is kept after an OLT delete and this prevents a meter to properly get re-installed on the device when it comes up again.
State is leftover in OltMeterService in a few places, when OLT goes through controlled disconnect. For example:
pendingMeters is not cleaned up
bpInfoToMeters is not immediately cleaned up. We depend on the call to MeterService to purgeMeters to return a notification of METER_REMOVED in order to clean up. Need explicit clean up of bpInfoToMeters. it is better to delete it from the store first, instead of waiting for confirmation of deletion, because otherwise someone may use it while you are waiting for deletion confirmation
Finally as I mentioned before, pendingRemoveMeters is not cleaned up immediately.