nfsd: restore NFSv3 ACL support

An error in e333f3bb left the nfsd_acl_program->pg_vers array empty,
which effectively turned off the server's support for NFSv3 ACLs.

Fixes: e333f3bb

 "nfsd: Allow containers to set supported nfs versions"
Cc: stable@vger.kernel.org
Cc: Trond Myklebust <trondmy@gmail.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>