Log a message when rules are reloaded

When the rules are reloaded, it is prudent to log a message. This will
help in the analysis of logs.

server/modules/filter/dbfwfilter/dbfwfilter.c

@@ -722,6 +722,7 @@ bool dbfw_reload_rules(const MODULECMD_ARG *argv)
         if (process_rule_file(filename, &rules, &users))
         {
             atomic_add(&inst->rule_version, 1);
+            MXS_NOTICE("Reloaded rules from: %s", filename);
         }
         else
         {