MXS-1312: Make the permission rule the default type

If a rule is defined with only an optional part, it should be of the
permission type. This type is used to signal that the rule matches if the
optional constraints are fulfilled.

Due to refactoring, the default type was changed from RT_PERMISSION to
RT_UNDEFINED.

server/modules/filter/dbfwfilter/dbfwfilter.c

@@ -1007,7 +1007,7 @@ bool create_rule(void* scanner, const char* name)
 
         if (ruledef && (ruledef->name = MXS_STRDUP(name)))
         {
-            ruledef->type = RT_UNDEFINED;
+            ruledef->type = RT_PERMISSION;
             ruledef->on_queries = QUERY_OP_UNDEFINED;
             ruledef->next = rstack->rule;
             ruledef->active = NULL;