Optimize the selection process for saving either AFS or Native ACLS by keeping track...

Optimize the selection process for saving either AFS or Native ACLS by keeping track of the filesystem we are doing a backup of. This way we don't have to check if a filesystem is still either AFS or not as when we know if it is all files on the same filesystem are either AFS or not. We also clear the native save flag when a filesystem says it doesn't support acls so we don't keep on trying saving acls on filesystem that don't support them.