tests: use `hg unbundle` instead of `hg pull` in some tests `hg pull <bundle>` uses the special "bundlerepo" repository. The bundlerepo code makes many assumptions about the storage of repositories. It will be difficult to teach bundlerepo to use non-revlog storage before a better storage interface is established. Many test failures using our "simple store" are related to bundlerepo: the simple store just isn't compatible with bundlerepo because of storage assumptions in bundlerepo. In order to mitigate the impact of bundlerepo on our code base, this commit changes various tests to use `hg unbundle` instead of `hg pull`. This bypasses the bundlerepo code. Tests exercising exchange functionality have not been altered, as they should be using `hg pull` and going through the bundlerepo code paths. Differential Revision: https://phab.mercurial-scm.org/D3059