BUG#13917335 - ASSERTION `REPORT_PORT != 0' FAILED IN NETWORK_INIT ()

Problem - The cause of the failure is mainly due to the assert added in
          the code as a result of the fix of the BUG-13333431. When we
          start the server with the --skip-networking option enabled
          we have the mysqld_port explicitly to 0. Since the value of
          report_port is set to mysqld_port, the assertion that
          (report_port!= 0) fails.

Fix - the fix of the problem is to assert the not zero value of
      report_port only in the case the --skip-networking option is not
      used to start the mysqld server.

sql/mysqld.cc:
  Added the code to check for the skip-networking option while starting
  the server.

sql/mysqld.cc

@@ -1830,7 +1830,12 @@ static void network_init(void)
   {
     report_port= mysqld_port;
   }
-  DBUG_ASSERT(report_port != 0);
+
+#ifndef DBUG_OFF
+  if (!opt_disable_networking)
+    DBUG_ASSERT(report_port != 0);
+#endif
+
   if (mysqld_port != 0 && !opt_disable_networking && !opt_bootstrap)
   {
     struct addrinfo *ai, *a;