chore: add backoff to dispatcher warning logs

This could be helpful to debug issues communicating with API.

Author: obycode

testnet/stacks-node/src/event_dispatcher.rs

@@ -455,7 +455,8 @@ impl EventObserver {
                 Err(err) => {
                     warn!(
                         "Event dispatcher: connection or request failed to {}:{} - {:?}",
-                        &host, &port, err
+                        &host, &port, err;
+                        "backoff" => backoff
                     );
                 }
             }