CLOUDSTACK-1469: Include JNA in the classpath when starting the Agent

This should have been already merged into 4.1, but didn't come through properly.

We use the JNA version shipped with CentOS 6.X since that works best with
libvirt 0.4.9
CLOUDSTACK-198: Included VpnUsers in Add state while listing. Added state to Vpn user response.
CLOUDSTACK-1738 : Adding code for StatsCollector initialization using spring framework. This was not initialized and hence stats were not colleced on vm, host and storage in CS.