FWTS: updated to check for Linux Kernel Lockdown patchset

FirmWare Test Suite (FWTS) has added awareness tests for the Linux Kernel Lockdown patchset. Eg:

Kernel is lockdown. Aborted.
Please unlock the kernel before you test the UEFI tests.
Make sure you disable secureboot and disable the kernel lockdown,
(by kernel parameter lockdown=None).

https://lists.ubuntu.com/archives/fwts-devel/2020-March/011725.html

https://launchpad.net/fwts