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)

parity/main.rs

@@ -117,6 +117,8 @@ fn start() -> Result<String, String> {
 }
 
 fn main() {
+	// Always print backtrace on panic.
+	::std::env::set_var("RUST_BACKTRACE", "1");
 	// just redirect to the sync::main()
 	if std::env::args().nth(1).map_or(false, |arg| arg == "sync") {
 		sync::main();