ofp-print: Don't abort on unknown reason in role status message.

A buggy or malicious switch could send a role status message with a bad
reason code, which if printed by OVS would cause it to abort.  This fixes
the problem.

Reported-by: Bhargava Shastry <bshastry@sec.t-labs.tu-berlin.de>
Signed-off-by: Ben Pfaff <blp@ovn.org>
Acked-by: Yi-Hung Wei <yihung.wei@gmail.com>

lib/ofp-print.c

@@ -2037,7 +2037,8 @@ ofp_print_role_status_message(struct ds *string, const struct ofp_header *oh)
         ds_put_cstr(string, "experimenter_data_changed");
         break;
     default:
-        OVS_NOT_REACHED();
+        ds_put_cstr(string, "(unknown)");
+        break;
     }
 }