[UPDATED] Reduce report of failed connection attempts

This applies to routes, gateways and leaf node connections.
The failed attempts will be printed at the first, after the first
minute and then every hour.
The connect/error statements now include the attempt number.

Note that in debug mode, all attempts are traced, so you may get
double trace (one for debug, one for info/error).

Resolves #969

Signed-off-by: Ivan Kozlovic <ivan@synadia.com>

server/leafnode.go

@@ -165,6 +165,9 @@ func (s *Server) connectToRemoteLeafNode(remote *leafNodeCfg) {
 
 	var conn net.Conn
 
+	const connErrFmt = "Error trying to connect as leaf node to remote server (attempt %v): %v"
+
+	attempts := 0
 	for s.isRunning() && s.remoteLeafNodeStillValid(remote) {
 		rURL := remote.pickNextURL()
 		url, err := s.getRandomIP(resolver, rURL.Host)
@@ -177,7 +180,11 @@ func (s *Server) connectToRemoteLeafNode(remote *leafNodeCfg) {
 			conn, err = net.DialTimeout("tcp", url, dialTimeout)
 		}
 		if err != nil {
-			s.Errorf("Error trying to connect as leaf node to remote server: %v", err)
+			attempts++
+			s.Debugf(connErrFmt, attempts, err)
+			if shouldReportConnectErr(attempts) {
+				s.Errorf(connErrFmt, attempts, err)
+			}
 			select {
 			case <-s.quitCh:
 				return