message: [cluster_test] Fix printing of health-check results
  After the health-check printing was printing one validator per line as seen below. This PR fixes it to old behaviour
  Ran --health-check on my workspace and verified the expected behaviour
  Related to
  Bug introduced by
  Closes:
  Approved by: andll
diff: @@ -141,17 +141,19 @@ impl HealthCheckRunner {
  }
  let mut failed = vec![];
  + let mut validators_message = "".to_string();
  for (i, (node, healthy)) in node_health.into_iter().sorted().enumerate() {
  if healthy {
  - messages.push(format!("{}* {}{} ", Fg(Green), node, Fg(Reset)));
  + validators_message.push_str(&format!("{}* {}{} ", Fg(Green), node, Fg(Reset)));
  } else {
  - messages.push(format!("{}* {}{} ", Fg(Red), node, Fg(Reset)));
  + validators_message.push_str(&format!("{}* {}{} ", Fg(Red), node, Fg(Reset)));
  failed.push(node);
  }
  if (i + 1) % 15 == 0 {
  - messages.push(format!(""));
  + validators_message.push_str("\n");
  }
  }
  + messages.push(validators_message);
  messages.push(format!(""));
  messages.push(format!(""));
  