Monitoring web interface is unavailable during hardware initialization

Summary

Currently, the GEM monitor application web interface is unavailable during hardware initialization (i.e. when the connections to the back-end boards are attempted). The initialization time can be significant, particularly if some AMC do not exist or do have an incorrect configuration.

This issue was raised in https://gitlab.cern.ch/cmsgemonline/cmsgemos/-/merge_requests/9#note_3408920.

Steps to reproduce

1. Launch a xDAQ process with the GEM monitoring application enabled
2. Go to the monitoring web page within the first 10-20 seconds
3. The CGI requests fail

What is the expected correct behavior?

The monitoring web interface should be available at all time. It should also be made clear to the user that the connections to the back-end boards are being attempted.

Relevant logs and/or screenshots

Environment

• Version used: !9 (merged) (94617894)
• Operation System: CC7 as installed on gem904daq04