The nsupdate system test did not record failures from the
'update_test.pl' Perl script. This was because the 'ret' value was
not being saved outside the '{ $PERL ... || ret=1 } cat_i' scope.
Change this piece to store the output in a separate file and then
cat its contents. Now the 'ret' value is being saved.
Also record failures in 'update_test.pl' if sending the update
failed.
Add missing 'n' incrementals to 'nsupdate/test.sh' to keep track of
test numbers.
(cherry picked from commit 5b31811b5f)
fd01889b8a