largefiles: fix check that ensures that --all-largefiles is only used locally Previously, the command added in the test failed with “abort: --all-largefiles is incompatible with non-local destination existing_destination”. The reason for the buggy behavior was the use of hg.islocal(), which does “return true if repo (or path pointing to repo) is local” and, for local paths, assumes that the path is actually pointing to an existing repository and returns whether the path is not a regular file (in which case it assumes that it is a bundlerepo, which are considered non-local).