Bad vcswatch action item with non-git repositories

@nthykier reported on IRC that the customdeb package has a vcswatch action item titled "None new commits since last upload, time to upload?". The long description also shows:

Here are the relevant commit messages: None

See https://tracker.debian.org/pkg/customdeb

The vcswatch.json file effectively doesn't contain any data in its "commits" and "vcslog" keys (they are set to the null value) when the VCS is not git ("vcs" key != git). We should fix the code and the template to behave in some better way.

We could for example replace the number of commits by "some" and display the log only if it is non-null. See distro_tracker/vendor/debian/tracker_tasks.py (UpdateVcsWatchTask.update_action_item) and distro_tracker/vendor/debian/templates/debian/vcswatch-action-item.html.