Runner idle/busy status command line switch
Description
It would be very useful if the gitlab-runner command had a switch that would list whether there is currently a job running or not.
Proposal
A command line switch for gitlab-runner like query (since status is already used to report if the service is running).
At minimum it could be a simple "true/false" or "idle/busy" kind of status message to show if the runner is idle or not.
Of course the runner status can be obtained from the GitLab API but often it would be more convenient to not give permissions to GitLab for doing it.
Allowing the runner itself to report its status seems logical and along the separation of ops responsibilities.
For example preparing for a server update, server reboot, maintenance, and other tasks the status of GitLab Runner needs to be taken into account to avoid interrupting running jobs. Often the responsibilities for such operations may be different from GitLab itself and granting permissions to the GitLab API for checking this seems unnecessary.