BUG/MINOR: acme: wrong dns-01 challenge in the log

BUG/MINOR: acme: wrong dns-01 challenge in the log

Since 861fe532046 ("MINOR: acme: add the dns-01-record field to the
sink"), the dns-01 challenge is output in the dns_record trash, instead
of the global trash.

The send_log string was never updated with this change, and dumps some
data from the global trash instead. Since the last data emitted in the
trash seems to be the dns-01 token from the authorization object, it
looks like the response to the challenge.

This must be backported to 3.2.