If we can't find a route to communicate, emit an error message rather than just exiting with a non-zero status

cmr=v1.7.5:reviewer=jsquyres:subject=print error if cannot communicate

This commit was SVN r30922.

orte/mca/oob/tcp/help-oob-tcp.txt

@@ -64,3 +64,13 @@ value will be ignored.
   Value:      %s
   Message:    %s
 #
+[unable-to-communicate]
+One or more TCP routes were given to a process, but no
+communication path could be found:
+
+  Source: %s
+  Peer:   %s
+
+This usually is caused by a lack of common network interfaces
+and no route found between them.
+  

orte/mca/oob/tcp/oob_tcp_component.c

@@ -1296,6 +1296,9 @@ void mca_oob_tcp_component_no_route(int fd, short args, void *cbdata)
         if (ORTE_SUCCESS != orte_routed.route_lost(&mop->hop)) {
             ORTE_ACTIVATE_PROC_STATE(&mop->hop, ORTE_PROC_STATE_LIFELINE_LOST);
         } else {
+            orte_show_help("help-oob-tcp.txt", "unable-to-commiunicate",
+                           true, ORTE_NAME_PRINT(ORTE_PROC_MY_NAME),
+                           ORTE_NAME_PRINT(&mop->hop));
             ORTE_ACTIVATE_PROC_STATE(&mop->hop, ORTE_PROC_STATE_COMM_FAILED);
         }
     }