nfs: interpret aclsupport attribute

It's not an interesting attribute but I've occasionally been annoyed by
having to look it up just to verify a server isn't doing something nuts.

Ping-Bug: 10649
Change-Id: I660b62039075a4044946e590ee75ed5690290bc5
Reviewed-on: https://code.wireshark.org/review/5146
Reviewed-by: Michael Mann <mmann78@netscape.net>