Stale etcd data in openolt adapter after olt device delete

There is below stale key in etcd after olt device delete

service/voltha/voltha_voltha/resource_manager/

{XGS-PON}

/

{2c6cafa5-c55b-4428-86d2-513ec1356860}

/onu_id_pool/

{0}

It seems like openolt device delete handling and ChildDeviceLost handling are having race condition where olt device delete cleans up all entries, but ChildDeviceLost may be creating entries again by updating the kv store during resource release.

A possible fix is to have the getDeviceDeletionInProgressFlag check to see if olt device delete is in progress and then ignore ChildDeviceLost handling if olt device delete is already in progress.

Logs are attached.