Remove update_volume_status log message from NFS driver

The manager logs an INFO message when this action occurs already,
and it not called by anyone else, so don't log twice:

INFO [cinder.volume.manager] Updating volume status
DEBUG [cinder.volume.drivers.nfs] Updating volume status

Change-Id: Id99be0c0e50837c2b59963d983b9a7db3d25919a
Merge "Remove update_volume_status log message from NFS driver"