Revert "nfsd: nfs4_file_get_access: need to be more careful with O_RDWR"

This reverts commit df66e753.

nfsd4_lock can get a read-only or write-only reference when only a
read-write open is available.  This is normal.

Cc: Harshula Jayasuriya <harshula@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>