Lustre clients are mounted with option acl,user_xattr

wipp-mds2@tcp:/WIPP /mnt/Lustre lustre defaults,acl, 0 0

to reproduce the problem

#!/bin/bash
rm -f dummy_file_test_xattr
touch dummy_file_test_xattr
chown nobody:nobody dummy_file_test_xattr
su -s/bin/bash nobody -c "setfacl -m g:bin:rw dummy_file_test_xattr"
su -s/bin/bash nobody -c "getfacl dummy_file_test_xattr"
su -s/bin/bash bin -c "setfattr -n user.test.xattr -v 123456 dummy_file_test_xattr"
su -s/bin/bash bin -c "getfattr -d dummy_file_test_xattr"

the output
setfattr: dummy_file_test_xattr: Operation not permitted