Remove return from rpc cast

This change removes return statement from rpc cast method calls.
As rpc cast are asynchronous, so doesn't return anything.

Change-Id: I766f64f2c086dd652bc28b338320cc94ccc48f1f

nova/compute/rpcapi.py

@@ -1503,7 +1503,7 @@ class ComputeAPI(object):
         client = self.router.client(ctxt)
         cctxt = client.prepare(server=_compute_host(None, instance),
                 version=version)
-        return cctxt.cast(ctxt, "trigger_crash_dump", instance=instance)
+        cctxt.cast(ctxt, "trigger_crash_dump", instance=instance)
 
     def cache_images(self, ctxt, host, image_ids):
         version = self._ver(ctxt, '5.4')

nova/conductor/rpcapi.py

@@ -473,4 +473,4 @@ class ComputeTaskAPI(object):
             raise exception.ServiceTooOld(_('nova-conductor too old'))
         kw = {'instance': instance, 'migration': migration}
         cctxt = self.client.prepare(version=version)
-        return cctxt.cast(ctxt, 'revert_snapshot_based_resize', **kw)
+        cctxt.cast(ctxt, 'revert_snapshot_based_resize', **kw)

nova/scheduler/rpcapi.py

@@ -171,15 +171,15 @@ class SchedulerAPI(object):
 
     def update_instance_info(self, ctxt, host_name, instance_info):
         cctxt = self.client.prepare(version='4.2', fanout=True)
-        return cctxt.cast(ctxt, 'update_instance_info', host_name=host_name,
-                          instance_info=instance_info)
+        cctxt.cast(ctxt, 'update_instance_info', host_name=host_name,
+                   instance_info=instance_info)
 
     def delete_instance_info(self, ctxt, host_name, instance_uuid):
         cctxt = self.client.prepare(version='4.2', fanout=True)
-        return cctxt.cast(ctxt, 'delete_instance_info', host_name=host_name,
-                          instance_uuid=instance_uuid)
+        cctxt.cast(ctxt, 'delete_instance_info', host_name=host_name,
+                   instance_uuid=instance_uuid)
 
     def sync_instance_info(self, ctxt, host_name, instance_uuids):
         cctxt = self.client.prepare(version='4.2', fanout=True)
-        return cctxt.cast(ctxt, 'sync_instance_info', host_name=host_name,
-                          instance_uuids=instance_uuids)
+        cctxt.cast(ctxt, 'sync_instance_info', host_name=host_name,
+                   instance_uuids=instance_uuids)