virt: Adds support for multi-host migration of system without serial console.

For multi-host migration system without serial console is
necessary to have bridge on hosts where guest should be
migrated in same network.

 _________                _________
|  host1  |              |  host2  |
|         |              |         |
| src br--|--------------|-dst br  |
|    |    |              |    |    |
|  |vm1|  |              |  |vm1|  |
|_________|              |_________|

Otherwise host2 couldn't connect to vm1 after migration.

Signed-off-by: Jiří Župka <jzupka@redhat.com>
virt: Adds multihost migration test for floppy ejecting.

Signed-off-by: Jiří Župka <jzupka@redhat.com>