protect file access if running

[GIC-de]

The BNG Blaster Controller endpoint GET: /api/v1/instances/<instance-name>/<file-name> allows to download some files from test instances. Here it is recommended to download files only if test instance is not running to prevent downloading corrupted files. This can be checked by polling GET: /api/v1/instances/<instance-name>.

NOTE: The BNG Blaster Controller access those files read only, so they are not corrupted on the server but the loaded artefact might be corrupted.

As an enhancement, the controller should prevent access to at least the following files if the instance is still running:

• run_report.json
• run.pcap

Those files will be very likely corrupted if accessed while running.