MXS-1346: Make dbfwfilter objects non-copyable

The User and Rule classes should not be copied.

server/modules/filter/dbfwfilter/rules.hh

@@ -20,8 +20,12 @@
  * Each type of rule has different requirements that are expressed as void pointers.
  * This allows to match an arbitrary set of rules against a user.
  */
-struct Rule
+class Rule
 {
+    Rule(const Rule&);
+    Rule& operator=(const Rule&);
+
+public:
     Rule(std::string name);
     virtual ~Rule();
     virtual bool matches_query(GWBUF* buffer, char** msg);

server/modules/filter/dbfwfilter/users.hh

@@ -33,8 +33,12 @@ typedef std::list<SUserTemplate>           TemplateList;
 /**
  * A user definition
  */
-struct User
+class User
 {
+    User(const User&);
+    User& operator=(const User&);
+
+public:
     User(std::string name):
         name(name),
         lock(SPINLOCK_INIT),