local key client does not return curve type

This breaks voting:

{"caller":"state.go:836","component":"Tendermint","err":"invalid curve type","height":1,"log_channel":"Info","message":"enterPropose: Error signing proposal","module":"consensus","round":0,"run_id":"ae20372c-68ab-11e8-827b-6da5986ff0ad","scope":"tendermint.NewNode","time":"2018-06-05T10:32:03.568661284Z"}

Signed-off-by: Sean Young <sean.young@monax.io>