MXS-1782: Add listener state to REST API

The state of each individual listener is now displayed in the REST
API. Created common functions for printing the listener state and took
them into use. Added the new state into MaxCtrl output.

maxctrl/lib/list.js

@@ -104,7 +104,8 @@ exports.builder = function(yargs) {
                 return getSubCollection(host, 'services/' + argv.service, 'attributes.listeners', [
                     {'Name': 'id'},
                     {'Port': 'attributes.parameters.port'},
-                    {'Host': 'attributes.parameters.host'}
+                    {'Host': 'attributes.parameters.host'},
+                    {'State': 'attributes.state'}
                 ])
             })
         })