tests/qtest/migration: Add migrate_set_ports into migrate_qmp to update migration...

tests/qtest/migration: Add migrate_set_ports into migrate_qmp to update migration port value

migrate_get_connect_qdict gets qdict with the dst QEMU parameters.

migrate_set_ports() from list of channels reads each QDict for port,
and fills the port with correct value in case it was 0 in the test.

Signed-off-by: Het Gala <het.gala@nutanix.com>
Suggested-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240312202634.63349-6-het.gala@nutanix.com
Signed-off-by: Peter Xu <peterx@redhat.com>