Merge ~mpontillo/maas:remove-es6-for-now into maas:master

[Mike Pontillo]

Remove ES6 (for now).

The team decided that to stick to ES5 JavaScript for now, to maintain consistency with existing code.

While I would personally prefer to keep the existing ES6 and continue to phase it in, this branch removes the ES6 that I have so far intentionally added.

[Lee Trager (ltrager)]

We should discuss allowing ES6 for next cycle as I agree phasing ES6 in would be a good way forward.

review: Approve

diff --git a/src/maasserver/static/js/angular/directives/maas_obj_form.js b/src/maasserver/static/js/angular/directives/maas_obj_form.js
index b2c394f..d98820c 100644
--- a/src/maasserver/static/js/angular/directives/maas_obj_form.js
+++ b/src/maasserver/static/js/angular/directives/maas_obj_form.js
@@ -555,7 +555,7 @@ angular.module('MAAS').directive('maasObjField', ['$compile',
                         " are required on maas-obj-field.");
                 }
                 if(angular.isString(attrs.disabled)) {
-                    scope.ngDisabled = () => true;
+                    scope.ngDisabled = function() { return true; };
                 }
 
                 // Remove transcluded element.
@@ -845,8 +845,8 @@ angular.module('MAAS').directive('maasObjField', ['$compile',
                         '</input>'
                     ].join(''));
                     inputElement = $compile(inputElement)(hiddenScope);
-                    scope.getValue = () => attrs.value;
-                    scope.updateValue = () => null;
+                    scope.getValue = function() { return attrs.value; };
+                    scope.updateValue = function() { return null; };
                 } else if(attrs.type === "onoffswitch") {
                     var switchScope = scope.$new();
                     switchScope._toggle = controller.registerField(