teor authored Jan 30, 2019 and Nick Mathewson committed Mar 12, 2019

Cleanup some bugs discovered during 23576:

* stop copying the first 20 characters of a 40-character hex string
  to a binary fingerprint
* stop putting IPv6 addresses in a variable called "ipv4"
* explain why we do a duplicate tt_int_op() to deliberately fail and
  print a value

Fixes bug 29243; bugfix on 0.3.2.1-alpha.