CueGUI builds are broken in Docker

[bcipriano]

Describe the bug CueGUI Docker builds fail to run tests due to an xvfb-run error:

/usr/bin/xvfb-run: line 181:    24 Segmentation fault      DISPLAY=:$SERVERNUM XAUTHORITY=$AUTHFILE "$@" 2>&1

This is happening in our CI pipelines but can be reproduced locally as well.

To Reproduce Steps to reproduce the behavior:

1. Run docker build -t opencue/cuegui -f cuegui/Dockerfile .
2. Build fails during unit test stage with above error.

Expected behavior Tests should pass and docker build should complete successfully.

Version Number 06d0b9a68f71e3cece6c66b4a5ea786464eef1f6