fix(tooltip): Use only once, don't use an empty transclusion fn

[Igosuki]

The additional $digest and empty transclusion seem unnecessary in 1.2 and are breaking changes in 1.3 (ng-class breaks).

[pkozlowski-opensource]

Thnx @Igosuki !

[chrisirhc]

@Igosuki , could you post a Plunker demonstrating this breakage? I don't see it and now this change actually causes symptoms demonstrated in #2935 . This change is actually incorrect as it never binds the template to a new scope after the first time it's linked, since no new clones are created.

I've checked the documentation and I don't see this breakage that you mention.
After reverting change, I also got the test case mentioned in #2935 working:
http://plnkr.co/edit/l49BH8DMwHqKuPjgZ5qn?p=preview

[chrisirhc]

I'll be reverting this change on master. If you have a test case for this change, please do post it so I can look into it.

[Igosuki]

Will do ! Just have to extract the test case from my app.

[chrisirhc]

@Igosuki , does #2951 demonstrate the issue you were having?

[Igosuki]

Hey @chrisirhc sorry I didn't get back to you on this. #2951 does demonstrate the exact problem.

And I don't see any issues upgrading to 0.12 with your merges.

[wesleycho]

Thanks for the find, I am closing this PR as it appears this is no longer an issue with the changes that have been made to the tooltip.