Put a tiny implementation for SimFilesystem in.
Put a tiny implementation for SimFilesystem in.

Throw out field in SimFilesystem that we're not using yet.

Signed-off-by: mulhern <7b51bcf507bcd7afb72bf8663752c0ddbeb517f6@redhat.com>

trgill/stratisd,mulkieran/stratisd,stratis-storage/stratisd,stratis-storage/stratisd,trgill/stratisd,stratis-storage/stratisd,mulkieran/stratisd