Add a force option

[kutschke]

The CI refuses to rerun the CI if, since the last CI run, there are neither intervening commits on the PR not changes to the HEAD of the repo. This means that if there is an external issue, such as a change to mu2e_trig_config or the DB server going down, we cannot rerun the CI.

We should add syntax to the CI launch command that forces the CI to run even if it would be blocked by those tests. I think it's OK if anyone who can relaunch the CI can also use the force option.