Openstorage volume attach call needs attachOptions as Parameter?

[ram-infrac]

Volume Create call accept passphrase and register it with spechandler, before calling Attach() we read the same and pass it as options to Attach call -

Attach(volumeID string, attachOptions map[string]string) (string, error)

While exposing this over grpc this will may or may not be case since Attach call can be separately called by grpc client while passing passphrase as argument.

So is it required that this options is always read from spechandler or not? If yes then we don't need option`` argument in Attach``` signature

[ram-infrac]

@lpabon