hgweb: construct static URL like hgweb does hgwebdir has a bit of code for constructing URLs. This reinvents wheels from our parsedrequest instance. And sometimes the behavior varies from what hgweb does. We'll want to converge that behavior. This commit changes hgwebdir so its staticurl template keyword is constructed the same way as hgweb's. There's probably room to factor this into a shared function. But let's solve the problem of divergence first. Differential Revision: https://phab.mercurial-scm.org/D2817