usnic: make this show_help message like the others

There's no need for the port number (since usNIC has no port numbers),
and make the wording the same as other help messages.

Reviewed by Reese Faucette.

cmr=v1.8.2:reviewer=ompi-rm1.8

This commit was SVN r32134.

ompi/mca/btl/usnic/btl_usnic_module.c

@@ -295,7 +295,6 @@ static int add_procs_create_ahs(ompi_btl_usnic_module_t *module,
                            true,
                            ompi_process_info.nodename,
                            ibv_get_device_name(module->device),
-                           module->port_num,
                            module->if_name,
                            mca_btl_usnic_component.arp_timeout);
             break;

ompi/mca/btl/usnic/help-mpi-btl-usnic.txt

@@ -240,7 +240,7 @@ application will likely either run with degraded performance and/or
 abort.
 
   Server:              %s
-  usNIC interface:     %s:%d (%s)
+  usNIC interface:     %s (which is %s)
   Current ARP timeout: %d (btl_usnic_arp_timeout MCA param)
 #
 [transport mismatch]