In the current V3 migration protocol, Libvirt does not
check the result of the function

  qemuMigrationVPAssociatePortProfiles

This means that it is possible for a migration to complete
successfully even when the VM loses network connectivity on
the destination host.

With this change libvirt aborts the migration
(during the "finish" step) when the above function fails, that
is to say when at least one of the port profile associations fails.

Signed-off by: Christian Benvenuti <benve@cisco.com>