Server endpoints should report number of active connections as a JMX operation

Even if JMX statistics are disabled, as a JMX operation, the server endpoints should expose the number of active connections on the endpoint.

Two operations should be exposed.

1. numberOfLocalConnections(), reporting a count of active connections on the node invoked.
2. numberOfGlobalConnections(), so that if invoked, it launches a distributed executor task to the entire cluster which does a count on each node and aggregates the result.

The second operation would allow a sysadmin to query a single node to get the number of open connections to the entire cluster.