Backports to beta v1.3.6 (#2571)

* v1.3.6

* Print backtrace on panic (#2535)

* Don't activate peers on connect; Test (#2537)

* Removing unwarps from sync module (#2551)

* Remove unwrap from client module (#2554)

* remove unwraps in client

* imporve block hash expect message

* mining perf trace

* Fixed race condition in trace import (#2555)