test: Kill podman pause process between tests

Working with user podman API leaves behind a `podman pause` process
which is not attached to/stopped by podman.service.

Avoid that leaking into the next test while the data directories get
restored.

See containers/podman#7180

test/check-application

@@ -63,6 +63,9 @@ class TestApplication(testlib.MachineCase):
         # Enable user service as well
         self.restore_dir("/home/admin/.local/share/containers")
         self.admin_s.execute("systemctl --now --user enable podman.socket")
+        # HACK: user podman.service leaks a "podman pause" outside of the unit: /~https://github.com/containers/podman/issues/7180
+        self.addCleanup(self.admin_s.execute, "pkill -u $USER -e podman; while pgrep -u $USER -a podman; do sleep 1; done")
+
         self.addCleanup(self.admin_s.execute, "podman rm --force --all; systemctl --user stop podman.service podman.socket")
 
         self.allow_journal_messages("/run.*/podman/podman: couldn't connect.*")