Redefining a domain via virDomainDefineXML should not give different results
based on an already existing definition.

Also, there's a crasher somewhere in the code:
https://bugzilla.redhat.com/show_bug.cgi?id=1739338

This reverts commit 94b3aa55Signed-off-by: NJán Tomko <jtomko@redhat.com>
Reviewed-by: NJiri Denemark <jdenemar@redhat.com>