nfs: fix xfstest generic/099 failed on nfsv3

After setxattr, the nfsv3 cached the acl which set by user.

But at the backend, the shared file system (eg. ext4) will check
the acl, if it can merged with mode, it won't add acl to the file.
So, the nfsv3 cached acl is redundant.

Don't 'set_cached_acl' when setxattr.

Signed-off-by: ZhangXiaoxu <zhangxiaoxu5@huawei.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>