Use compute rpcapi in nova-manage.

Part of bug 1006467.

This patch fixes nova-manage to use the compute rpcapi instead of
calling rpc.cast() directly.  This cast was actually broken, as it sent
an instance ID instead of UUID, so this change should make this code
functional again.

Change-Id: I90a1bf4a03cc6d9e21f24f19165141f894b6ec75

bin/nova-manage

@@ -80,6 +80,7 @@ from nova.api.ec2 import ec2utils
 from nova.auth import manager
 from nova.compat import flagfile
 from nova.compute import instance_types
+from nova.compute import rpcapi as compute_rpcapi
 from nova import context
 from nova import crypto
 from nova import db
@@ -1169,13 +1170,9 @@ class VolumeCommands(object):
             print "volume is not attached to an instance"
             return
         instance = db.instance_get(ctxt, volume['instance_id'])
-        host = instance['host']
-        rpc.cast(ctxt,
-                 rpc.queue_get_for(ctxt, FLAGS.compute_topic, host),
-                 {"method": "attach_volume",
-                  "args": {"instance_id": instance['id'],
-                           "volume_id": volume['id'],
-                           "mountpoint": volume['mountpoint']}})
+        rpcapi = compute_rpcapi.ComputeAPI()
+        rpcapi.attach_volume(ctxt, instance, volume['id'],
+                             volume['mountpoint'])
 
 
 class InstanceTypeCommands(object):