[#6640] Can't post vote counts with ticket update

Signed-off-by: Tim Van Steenburgh <tvansteenburgh@gmail.com>
[#6626] ticket:427 Use HEAD revision as default for SVN
[#6626] ticket:427 Returned use of url_for_commit() in controller
[#6626] ticket:427 Handle HEAD in url_for_commit for svn