DYNDNS: Retry also on timeouts
There is the dyndns_server option that is supposed to make it possible
for the admin to select a server to update DNS with if the server
detected by nsupdate does not work. The fallback works OK for the case
where nsupdate fails with a non-zero return code, but doesn't work
for the case where nsupdate times out.
This patch extends the retry condition to also fallback to the
dyndns_server directive if nsupdate return ERR_DYNDNS_TIMEOUT.
Reviewed-by: Fabiano Fidêncio <email@example.com>