Change metrics endpoint of Connect REST Extensions to use the MBeanServerv directly instead of HTTP calls to the Jolokia endpoint. Maybe also change the response format.

• remove proxying of the Jolokia client and return values directly from MBeanServer/MBeanServerConnection (alternatively add proper Jolokia endpoint configuration to the Kafka Connect config, is this maybe already available inside of Kafka Connect runtime options?!)
  (see example http://hirt.se/blog/?p=630 for reading local JMX metrics)