nfsd: Fix handling of attributes during Open/Create/Exclusive_41

When an NFSv4.n client specifies settings for attributes other
mode during a Open/Create/Exclusive_41, these other attributes
were not being set.

This patch resolves the problem by calling nfsrv_fixsattr()
after the VOP_CREATE() call in nfsvno_open() for this case.

There is no extant NFSv4.n client that currently does this,
as far as I know.

MFC after: 2 weeks