Update osi.py
Update osi.py

Hook's should not have more than one decorator attached
Ubuntu-Solutions-Engineering/juju-layer-osi,Ubuntu-Solutions-Engineering/juju-layer-osi,battlemidget/charm-osi-single,Ubuntu-Solutions-Engineering/juju-charm-osi,Ubuntu-Solutions-Engineering/juju-charm-osi,battlemidget/charm-osi-single