Change the method name from isConnected to Connected in the db api

Saw the following error while fetching the logical plan on AdsDimensionOperator:

Unexpected error: com.sun.jersey.api.client.UniformInterfaceException: GET http://node29.morado.com:57241/ws/v1/stram/logicalPlan returned a response status of 404 Not Found

As discussed with David the resolution is to change the isConnected() in db api to connected()