fix($animate): wait two until two digests are over until enabling animations

Even when no remote templates are to be downloaded, wait two digests until
enabling animations since all structural digests perform a post digest before
running animations.

Closes #8844


Broken Example (no remote templates -> `snapshot`):
http://plnkr.co/edit/LREaTTieMJj4lOPJTjI0?p=preview

Working example (no remote templates -> `this fix`):
http://plnkr.co/edit/CuigpbMIB4ZkdmhWJ1bO?p=preview

Working example (remote templates -> `snapshot`)
http://plnkr.co/edit/QLD5TVtWnHGvCLnFcCYw?p=preview

Working example (remote templates -> `this fix`)
http://plnkr.co/edit/YtjFzsb7bR2AwfXD9lF2?p=preview
can you call this `deregisterWatch` instead?