rbt post: checking repository info on server does not work anymore

The rbt post code didn't use the find_server_repository_info methods, which
were very useful for handling additional repository matching methods for
clearcase and SVN.

This also fixes the ClearCaseRepositoryInfo call from clearcase.py (3rd
parameter is vobstag, I suppose "uuid" was an old copy paste from svn
implementation).

Testing Done:
- Can post review request from any clearcase vob using rbt post 0.5.x.
- Tested on release-0.5.x => rbt post works but breaks post-review.
- Ran unit tests.

Bugs closed: 3533

Reviewed at https://reviews.reviewboard.org/r/6233/
Merge branch 'release-0.6.x'