So far setting the luks= attribute on a live image build had
no impact to the generated ISO image. This commit adds the
encryption capability also for live ISO images. The read-only
part of the rootfs gets encrypted using the provided luks
passphrase. An eventual persistent storage area gets encrypted
at boot time if the rd.live.encrypt kernel cmdline parameters
is passed. encryption/decryption requires to interactively
set/provide passhphrase information at boot time. Please note
due to the read-only restrictions of an ISO image there is no
way to apply the standard re-encryption process as it is
usually performed by kiwi encrypted systems. As such the
specified luks passphrase in the kiwi image descriptions
becomes sensitive information that needs to be protected
cce59eea28