fleet: make fleetctl path configurable
fleet: make fleetctl path configurable

mjg59/mantle,dm0-/mantle,marineam/mantle,dm0-/mantle,glevand/coreos--mantle,marineam/mantle,mischief/mantle,glevand/coreos--mantle,quantum/coreos-mantle,quantum/coreos-mantle,mischief/mantle,mjg59/mantle