btl/openib: fix coverity issue

CID 1269821 Dereference null return value (NULL_RETURNS)

This is another false positive that can be silenced by looping on
opal_list_remove_first instead of using both opal_list_is_empty and
opal_list_remove_first.

Signed-off-by: Nathan Hjelm <hjelmn@lanl.gov>

opal/mca/btl/openib/btl_openib_endpoint.c

@@ -613,13 +613,13 @@ void mca_btl_openib_endpoint_connected(mca_btl_openib_endpoint_t *endpoint)
     opal_progress_event_users_decrement();
 
     if(MCA_BTL_XRC_ENABLED) {
-        while(master && !opal_list_is_empty(&endpoint->ib_addr->pending_ep)) {
-            ep_item = opal_list_remove_first(&endpoint->ib_addr->pending_ep);
-            ep = (mca_btl_openib_endpoint_t *)ep_item;
-            if (OPAL_SUCCESS !=
-                opal_btl_openib_connect_base_start(endpoint->endpoint_local_cpc,
-                                                   ep)) {
-                BTL_ERROR(("Failed to connect pending endpoint\n"));
+        if (master) {
+            while (NULL != (ep_item = opal_list_remove_first(&endpoint->ib_addr->pending_ep))) {
+                ep = (mca_btl_openib_endpoint_t *)ep_item;
+                if (OPAL_SUCCESS !=
+                    opal_btl_openib_connect_base_start(endpoint->endpoint_local_cpc, ep)) {
+                    BTL_ERROR(("Failed to connect pending endpoint\n"));
+                }
             }
         }
         OPAL_THREAD_UNLOCK(&endpoint->ib_addr->addr_lock);