NFSD: Set the attributes used to store the verifier for EXCLUSIVE4_1

According to rfc5661 18.16.4,
"If EXCLUSIVE4_1 was used, the client determines the attributes
 used for the verifier by comparing attrset with cva_attrs.attrmask;"

So, EXCLUSIVE4_1 also needs those bitmask used to store the verifier.

Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>