Fix regressions introduced by the refactoring in 6.10.1:
- Logging does not include error message (e.g. "Connection refused" or "Timeout"), only number of retrieved SCTs, when "Min SCT" condition is not satisfied.
- Submission does not abort after "Max SCTs" condition is reached (but excess SCTs are still discarded)
- There's a limit of two parallel connections per log => More connections can lead to a timeout. This limit existed before 6.10.1, but wasn't reached as often. This limit should be increased to something high like 20 or 50.