linuxlive 0.4.2: room for large distros

The install test gives the virtual PC a 64 GB disk instead of 20 GB, so large distros (Tiki Head Linux, a GIS workstation, needs 22 GB) are installed and tested too. The disk is qcow2 and grows only as the install writes, so small distros cost nothing extra. To upgrade, change @v0.4.1 to @v0.4.2 in your workflow.