[Time Conductor] Fix date picker toggle

nasa/openmctweb#297; avoid flag toggled to display date-time
picker becoming lost in a child scope.

platform/commonUI/general/res/templates/controls/datetime-field.html

@@ -6,10 +6,10 @@
     </input>
     <a class="ui-symbol icon icon-calendar"
        ng-if="structure.format === 'utc' || !structure.format"
-       ng-click="pickerActive = !pickerActive">
+       ng-click="picker.active = !picker.active">
     </a>
-    <mct-popup ng-if="pickerActive">
-        <div mct-click-elsewhere="pickerActive = false">
+    <mct-popup ng-if="picker.active">
+        <div mct-click-elsewhere="picker.active = false">
             <mct-control key="'datetime-picker'"
                          ng-model="ngModel"
                          field="field"

platform/commonUI/general/src/controllers/DateTimeFieldController.js

@@ -69,9 +69,12 @@ define(
                 updateFromModel($scope.ngModel[$scope.field]);
             }
 
+            $scope.picker = { active: false };
+
             $scope.$watch('structure.format', setFormat);
             $scope.$watch('ngModel[field]', updateFromModel);
             $scope.$watch('textValue', updateFromView);
+
         }
 
         return DateTimeFieldController;

platform/commonUI/general/test/controllers/DateTimeFieldControllerSpec.js

@@ -91,6 +91,10 @@ define(
                 expect(mockScope.textValue).toEqual("1977-05-25 17:30:00");
             });
 
+            it("exposes toggle state for date-time picker", function () {
+                expect(mockScope.picker.active).toBe(false);
+            });
+
             describe("when user input is invalid", function () {
                 var newText, oldValue;