Make test suites configurable in netboot image

[ricardon]

Currently LUV.cfg holds parameters to configure netconsole, submission of results to a server as well the test suites that are executed. Making these edition is trivial in USB thumb drives as one only has to mount the drive, navigate to the file and edit it. Not so ease with netboot images.

Fortunately, we have the script modify_luv_netboot_efi.py that can modify various parameters in LUV.cfg (e.g., netconsole). This script can be extended to also modify what test suites are executed.