qemu: Fix checking of guest ABI compatibility when reverting snapshots

qemu: Fix checking of guest ABI compatibility when reverting snapshots

When reverting a live internal snapshot with a live guest the ABI
compatiblity check was comparing a "migratable" definition with a normal
one. This resulted in the check failing with:

revert requires force: Target device address type none does not match source pci

This patch generates a "migratable" definition from the actual one to
check against the definition from the snapshot to avoid this problem.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1006886