nfsd: Do not accept audit/alarm ACEs for the NFSv4 server

The UFS and ZFS file systems only support Allow/Deny ACEs
in the NFSv4 ACLs. This patch does not allow the server
to parse Audit/Alarm ACEs. The NFSv4 client is still
allowed to pase Audit/Alarm ACEs, since non-FreeBSD NFSv4
servers may use them.

This patch should not have a significant effect, since the
UFS and ZFS file systems will not handle these ACEs anyhow.
It simply serves as an additional "safety belt" for the
NFSv4 server.

MFC after: 2 weeks