Don't add the Encryption Storage Wrapper if there are no encryption modules

fixes #4125

If there is no encryption module enabled it makes no sense to setup the
encryption wrapper (because we can't do anything anyway).

This saves reading the header of files.
Especialy on external storage/objectstore this should improve
performance

Signed-off-by: Roeland Jago Douma <roeland@famdouma.nl>