Add links to DESY grafana for running jobs in serve_overview

Description

Especially when jobs are running unexpectedly long, it seemed useful to have a quick and easy way to see the corresponding node monitoring for this job on DESY's Grafana. This MR generates a suitable link for each running job. Unfortunately a call to squeue is required to obtain the node name.

Also fixes a small bug that got introduced some time ago, which caused pending jobs to also appear green.

How Has This Been Tested?

Since it's still maintenance, I decided to take the risk and use the currently running jobs for p2834 as a test case: http://max-exfl-cal001.desy.de:8008/

Types of changes

• New feature (non-breaking change which adds functionality)

Checklist:

• My code follows the code style of this project.

Reviewers

@kluyvert @ahmedk