fix(ngMock.$interval): should use angular.isDefined
fix(ngMock.$interval): should use angular.isDefined

The newly introduced `$interval` mock service for ngMock calls `isDefined`
in the global namespace which fails when used within unit tests.

This change adds the missing `angular.` prefix to such `isDefined` calls.

Closes #4334
Closes #4353

ammula88/angular.js,ammula88/angular.js,ammula88/angular.js,ammula88/angular.js,ammula88/angular.js