qemu: Set correct migrate host in client_migrate_info

qemu: Set correct migrate host in client_migrate_info

https://bugzilla.redhat.com/show_bug.cgi?id=920441

Currently, we are discarding listen attribute from qemu cookie even though
we strive to gather it. This result in not so cool bug: if user have
different networks, one for management/migration, and one for VNC/SPICE we
pass incorrect host to the qemu in client_migrate_info. What we actually
pass is remote hostname, while we should be passing remote listen address.
It doesn't matter as long as these two are the same, but they don't need
necessary to be like that.