configfile: always validate all scrypt parameters
configfile: always validate all scrypt parameters

This makes sure we cannot get weak parameters passed through a
rougue gocryptfs.conf.

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