Unfortunately there is not a way to do this with 'cold' migration. You can specify a server with live-migration though.

For 'cold' migration, as a workaround you can disable the nova-compute service on all of the nodes you don't want to migrate to. This ensures the scheduler only finds one valid host for the instance to go to.

nova service-disable <hostname> nova-compute

This only marks the service down on the controller side, it won't actually mess with instances or traffic (however this prevents those servers from being managed).

Once the scheduler has picked your desired host you can reenabled all of the services you disabled.

I have toyed with the idea of using nova evacuate <instance-id> <target-compute-host> to do this, but it would require shared storage for everything (since this won't actually move any data over). And this will probably leave some cruft on the original compute host since it won't issue any cleanup operations. But its cleaner that disabling all the other services.

Use evacuate at your own risk. You can easily lose data with it.

Poonam Agarwal has answered with how to specify a host with live-migration. Be aware that many factors make live-migration unreliable. In the case of block_migration you can dirty data faster than it can tranfer leaving you with a perpetually migrating image.