This routine migrates a communication identifier to the specified event
channel and moves any pending events associated with the rdma_cm_id
to the new channel. Users should not poll for events on the
rdma_cm_id's current event channel or invoke other routines on the
rdma_cm_id while migrating between channels. This call will block while
there are any unacknowledged events on the current event channel.
If the channel parameter is NULL, the specified rdma_cm_id will be
placed into synchronous operation mode. All calls on the id
will block until the operation completes.