Sometimes it is necessary to modify the kernel command-line of the
image, this adds support for a [customizations.kernel] section to the
blueprint:
[customizations.kernel]
append = "nosmt=force"
This will be appended to the kickstart's bootloader --append argument.
Includes tests for modifying the bootloader line, the kickstart
template, and examining the final-kickstart.ks created for a compose.
Related: rhbz#1688335
