Msf DNS server - add :use_resolver? method

Author: RageLtMan

lib/msf/core/exploit/dns/server.rb

@@ -166,6 +166,13 @@ def reset_service
     start_service
   end
 
+  #
+  # Determines if resolver is available and configured for use
+  #
+  def use_resolver?
+    !datastore['DISABLE_RESOLVER'] and self.respond_to?(:setup_resolver)
+  end
+
 end
 end
 end