kickstart-tests currently do not provide a way to log messages from early boot (kernel + initramfs phase).

Implement a support for logging such messages. The idea is to add a serial device that will write the output to a file:

virt-install .... --serial file,path=FILENAME

When the installation finishes, the file with the serial output is provided together with the other installation log files.

The kernel command line of the installed system will also need to be extended to use the serial device, for example:

console=ttyS0

Console messages should be gathered also from a boot of the installed system and submitted as a separate log file.

The purpose of this enhancement is to:

• make debugging of kernel/initramfs issues easier
• be able to parse the serial output file for expected errors. This would allow to write tests that intentionally fails in the initramfs phase (but that's not part of this task)