rdma: (fix) do not use cq_entry.len in send completions

According to libfabric specs, the len field in a completion entry
only applies to completed receive operations. We were using it for send
completions as well, which is currently working in the EFA provider,
but there is no guarantee that this will be true in the future and for
other providers.

Signed-off-by: Amedeo Sapio <asapio@amazon.com>

src/nccl_ofi_rdma.c

@@ -1433,7 +1433,7 @@ static inline int process_completions(struct fi_cq_data_entry *cq_entry, uint64_
 
 			if (req->type == NCCL_OFI_RDMA_SEND_CONN || req->type == NCCL_OFI_RDMA_SEND_CONN_RESP) {
 				/* CONN or CONN_RESP send completion */
-				ret = inc_req_completion(req, cq_entry[comp_idx].len, 1);
+				ret = inc_req_completion(req, sizeof(nccl_ofi_rdma_connection_info_t), 1);
 
 			} else if (req->type == NCCL_OFI_RDMA_SEND_CTRL) {
 				/* CTRL message send completion */