MFC: r227543

MFC: r227543
Modify the new NFS client so that nfs_fsync() only calls ncl_flush()
for regular files. Since other file types don't write into the
buffer cache, calling ncl_flush() is almost a no-op. However, it does
clear the NMODIFIED flag and this shouldn't be done by nfs_fsync() for
directories.

git-svn-id: svn://svn.freebsd.org/base/stable/8@229365 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f