Add temp symlinks to old TPL location (TriBITS #26)

I order to smooth the transition to the new TriBITS structure, the old
directory and find modules (symlinks) are restored.  This will allow me to
push the updated TriBITS and then we can work on getting the various
components to update their TPLsList.cmake files to point to the new locations.
Make repo update robust to forced branch updates

This changes to do the following for each git repo:

$ git clean -fdx
$ git fetch
$ git reset --hard <tracking_branch>

I tested this manually by running one of the VERA CTest driver scripts and
verified that it does indeed clean out the untracked and ignored files and it
resets the branch correctly.  This requires that each repo be on the correct
branch.  If it is not, then the script should return false.

I also upated the unit tests for this.  They are a little stronger but not
fantastically strong.
Make update of outer extra repos robust to forced branch pushes

This change should make the update of extra repos (like TriBITS in the VERA
build) robust to forced branch pushes of the tracking branch.

Here I just broke out the code that was being used for this in
TribitsCTestDriverCore.cmake and put it in TribitsUpdateExtraRepo.cmake.
Fix broken test after adding TIMEOUT to fetch