Description of problem:
Due to recent changes where node handler may also handle adding back pods, there can be a simultaneous add of the same pod, resulting in an error like:

0723 03:34:51.835876       1 ovn.go:502] error while creating logical port openshift-network-diagnostics_network-check-target-fh8bq error: Transaction Failed due to an error: constraint violation details: Transaction causes multiple rows in "Logical_Switch_Port" table to have identical values (openshift-network-diagnostics_network-check-target-fh8bq) for index on column "name".  First row, with UUID eed1ddd5-baaa-4d27-a89c-d0755d18d15e, existed in the database before this transaction, which modified some of the row's columns but not any columns in this index.  Second row, with UUID ab893aae-4dea-4a29-a6b8-513f93b7bfc7, was inserted by this transaction. in committing transaction

To reproduce it, simply restart the active ovnkube-master (ensure it becomes active again). The node handler will try to add back the pods at the same time the pod handler does, leading to the above error.