1. Fixed a bug, which reads certs even TLS is disabled
2. Persists Stratum TCP connection with auto-reconnect.
(retry backoff increases from 1s to 60s maximum)
3. Stratum update jobs on previous notifications are canceled
when a new notification arrives.
Usually, the jobs are so short and completed immediately.
However, if the Stratum connection is broken, this prevents
the bridge from accumulating stale jobs.
