tests: make output comaptible with hash changes in hg-4.8 46da52f4b820 in core mercurial added logic to try hard to reuse manifest if we can. In the tests of hgsubversion, there are lot of cases we create an empty commit with just branch name changed. In hg < 4.8, hgsubversion used to create a new manifest entry for that commit but after that patch, empty commit started using the manifest of the parent leading to hash change.