buildah bud tests under podman-remote

New functionality -- mostly in the diffs we apply to
buildah's helpers.bash -- to enable running buildah-bud
tests under podman-remote. The gist of it is, we start
a 'podman system service' before each test, and clean
it up on test exit.

Design decision: the diff file for helpers.bash is no
longer trailing-whitespace-clean: that ended up producing
diffs that git wouldn't apply, because in some cases
the whitespace is actually important. In order to pass CI,
we need to exclude this file from some checks.

Signed-off-by: Ed Santiago <santiago@redhat.com>

.pre-commit-config.yaml

@@ -4,8 +4,15 @@ repos:
   - repo: https://github.com/pre-commit/pre-commit-hooks.git
     rev: v3.4.0
     hooks:
+      # buildah-tests.diff is generated by 'git format-patch' and includes
+      # trailing whitespace as part of its format. We can work around that,
+      # but unfortunately the buildah repo has some files with tabs, which
+      # git-diff formats as '[+/-]<space><tab>', which these hooks choke on.
+      # Just disable checks on this diff file as a special case.
       - id: end-of-file-fixer
+        exclude: test/buildah-bud/buildah-tests.diff
       - id: trailing-whitespace
+        exclude: test/buildah-bud/buildah-tests.diff
       - id: mixed-line-ending
       - id: check-byte-order-marker
       - id: check-executables-have-shebangs