NFSv3: Fix another acl regression

When creating a new object on the NFS server, we should not be sending
posix setacl requests unless the preceding posix_acl_create returned a
non-trivial acl. Doing so, causes Solaris servers in particular to
return an EINVAL.

Fixes: 013cdf1088d72 (nfs: use generic posix ACL infrastructure,,,)
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1132786
Cc: stable@vger.kernel.org # 3.14+
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>