Close an event communication channel.
(struct rdma_event_channel *channel);
The communication channel to destroy.
Release all resources associated with an event channel and closes the
associated file descriptor.
Returns 0 on success, or -1 on error. If an error occurs, errno will be
set to indicate the failure reason.
All rdma_cm_id's associated with the event channel must be destroyed,
and all returned events must be acked before calling this function.