Code review comment for lp:~leonardr/launchpad/multiversion-wadl

OK, one more. My earlier fix to xx-branchmergeproposal broke a whole lot of other tests because it changed the ways all URLs were generated, just for the sake of one test. This update reverts the change to canonical_url() and instead changes xx-branchmergeproposal to use the standard way of generating web service URLs from a browser-initiated request.

The problem here is that the web service URLs generated by a browser-initiated request look like "http://launchpad.dev/api/". Ordinarily this is fine, but xx-branchmergeproposal generates URLs from a browser-initiated request and then passes them into a web service client that expects URLs that look like "http://api.launchpad.dev/". Rather than try to come up with a standard way of doing this, I created a helper method in the test that does the translation.

This branch also upgrades the version of lazr.restful used. I'm not 100% sure that this new version of lazr.restful is necessary, and I'm going to do some preliminary tests with the old version before landing.

Incremental diff: http://pastebin.ubuntu.com/387107/