MXS-2984: Fix list listeners

Backported the changed from 2.5 to 2.3 and added a test case.

maxctrl/test/diagnostics.js

@@ -42,6 +42,16 @@ describe("Diagnostic Commands", function() {
         });
     })
 
+    it('MXS-2984: Malformed `list listeners` output', function() {
+        return doCommand('list listeners RW-Split-Router --tsv')
+            .then(res => {
+                var d = res.split('\t')
+                d[0].should.equal('RW-Split-Listener')
+                d[1].should.equal('4006')
+                d[2].should.equal('::')
+            })
+    });
+
     after(stopMaxScale)
 });