test: explicitly "add" file before some commit in test-filecache.py `hg commit -A` will revert the `hg addremove` step if the commit fails. However `hg rollback` currently does not. We are about to improve internal consistency around transaction and dirstate and the behavior of `hg rollback` will align on the other behavior in the process. Before doing so, we make sure the test is using a separate call to `hg add` to avoid the test scenario to be affected by that future change. note: the behavior change for `hg rollback` seems fine as it affect a niche usecase and `hg rollback` usage have been strongly discouraged for a while.