Update LUKS post-install for Qubes 4.1.0

The updated version of Fedora that Qubes 4.1.0 ships with comes with a new version of anaconda based on python 3.8. Many parts of the base pyanaconda scripts have been rewritten from their previous versions and in some cases moved around.

This update adapts the changes I made to 4.0.4 pyanaconda to the new scripts. This is also using a slightly modified version of ks.cfg from upstream that doesn't include all of the nitrokey bits we don't need.

Finally I tweaked make-image.sh so that it clears out the purism/ directory in the unpackaged-iso workspace so that old versions of anaconda scripts from previous builds won't stick around.