fusefrontend: get rid of last hardcoded "gocryptfs.diriv" instances
fusefrontend: get rid of last hardcoded "gocryptfs.diriv" instances

Makes it easier to change the name (as some people want to):
https://github.com/rfjakob/gocryptfs/issues/37

rfjakob/gocryptfs,rfjakob/gocryptfs,rfjakob/gocryptfs,rfjakob/gocryptfs