engine: Explicitly name sysprep options

Previously virt-sysprep ran all known operations, but this destroyed the
initial-setup dialog. To prevent this, we now name the operations to
run.

Change-Id: Id0354c60cd437ea41ee09a82139a7b2a7ac27f9e
Signed-off-by: Fabian Deutsch <fabiand@fedoraproject.org>