gitrepo: provide the original opargs to exchange.push when repo is not gitrepo

We got a report in evolve/topic extension that hg push --publish was broken when both topic and hggit was enabled. Disabling either of them made it work again. When searching what could've went wrong, I noticed that opargs provided to exchange.push() don't contain 'publish': True anymore, here's the reason. This is a solution to the issue, it might not be enough in all situations, but it seems to be the correct thing to do in this particular block of code.

This call of orig() is only when repo is not gitrepo, IOW it's only for regular Mercurial repos.