Oops--in 916d2d844a I moved some constants into an array for
convenience, but here I'm accidentally writing to that array.
The effect is that if you ever encounter a filesystem lacking support
for ACLs or security labels, then all queries of supported attributes
will report that attribute as unsupported from then on.
Fixes: 916d2d844a "nfsd: clean up supported attribute handling"
Signed-off-by: J. Bruce Fields <bfields@redhat.com>