nfsd4: treat more recall errors as failures

If a recall fails for some unexpected reason, instead of ignoring it and
treating it like a success, it's safer to treat it as a failure,
preventing further delgation grants and returning CB_PATH_DOWN.

Also put put switches in a (two me) more logical order, with normal case
first.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>