QEMU health check can fill the root partition

Issue Background

I was trying to edit a test but couldn't save it due to disk being full

Issue description

Investigation revealed the QEMU health check was running with this disk usage

sudo du -h --max-depth=1 /var/lib/lava/dispatcher/tmp
963M    /var/lib/lava/dispatcher/tmp/57
963M    /var/lib/lava/dispatcher/tmp

The issues seems to be cause by an upstream bug

Acceptance criteria

• Describe the workaround in the Known issues page

Originally, the acceptance criteria was:

• We need to either not install the QEMU health check or prevent it from running when the user is attempting to test