fix(instances): find known VMs by UUID, not by name

Instance.proxy looked the domain up by its stored name. After a rename
or a name swap outside WebVirtCloud, an operation on one VM changed
another; after a VM was replaced under the same name, operations hit
the new VM.

wvmInstance takes the UUID and uses lookupByUUIDString, with no
fallback to the name: a missing UUID fails instead of picking another
domain. Every caller that has an Instance passes it: proxy, console,
quota, post-migration autostart and the VDI URL. Migration uses the
domain the proxy already resolved. getvvfile and the gstfsd requests
use the host's current name of that UUID.

Live tests cover a name swap and a VM replaced under the same name;
both fail on the previous code.

console/views.py

@@ -99,6 +99,7 @@ def console(request):
             instance.compute.password,
             instance.compute.type,
             instance.name,
+            uuid=instance.uuid,
         )
         console_type = conn.get_console_type()
         console_websocket_port = conn.get_console_websocket_port()