Commit id '1dac5fbb' removed xenmigr as a capability option
for virCapabilitiesAddHostMigrateTransport but didn't update
the schema resulting in possible failure for virt-xml-validate.
Signed-off-by: John Ferlan <jferlan@redhat.com>
ACKed-by Michal Privoznik <mprivozn@redhat.com>