Better error message on bind to non-rdma interface

Change-Id: Ia70020e37de6d94dfbf568404557b54e1b7f61d6

Author: petro-rudenko

src/main/java/org/apache/spark/shuffle/rdma/RdmaNode.java

@@ -81,11 +81,8 @@ class RdmaNode {
         logger.info("Failed to bind to port {} on iteration {}", bindPort, i);
         bindPort = bindPort != 0 ? bindPort + 1 : 0;
       }
-      if (err != 0) {
-        throw new IOException("Unable to bind, err: " + err);
-      }
 
-      if (listenerRdmaCmId.getVerbs() == null){
+      if (err != 0 || listenerRdmaCmId.getVerbs() == null){
         throw new IOException("Failed to bind. Make sure your NIC supports RDMA");
       }