Not enough disk space on ON1-OpenNebula

Background

Following commits have added deletion of tier2 images when ever coin is restarted:

• https://codereview.qt-project.org/#/c/214221/
• https://codereview.qt-project.org/#/c/214303/2

Grafana CI monitoring page confirms that feature is active:

• https://testresults.qt.io/grafana/d/000000043/continuous-integration-health
• Coin restart seems to reduce the disk usage to about 70%

Problem

Pretty soon after deleting old tier2 images the disk usage shoots back up to about 90% (and over). This means we have more active tier2 images in use than we really have disk space for.

Suggestion

Add 2TB more space to the /srv/vmdisks of on1-opennebula01.ci.qt.io