NFSv4.1: Use the more efficient open_noattr call for open-by-filehandle

When we're doing open-by-filehandle in NFSv4.1, we shouldn't need to
do the cache consistency revalidation on the directory. It is
therefore more efficient to just use open_noattr, which returns the
file attributes, but not the directory attributes.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>