builder/common: only count handshake error if auth tried

builder/common/step_connect_ssh.go

@@ -8,6 +8,7 @@ import (
 	"github.com/mitchellh/packer/communicator/ssh"
 	"github.com/mitchellh/packer/packer"
 	"log"
+	"strings"
 	"time"
 )
 
@@ -133,7 +134,14 @@ func (s *StepConnectSSH) waitForSSH(state map[string]interface{}) (packer.Commun
 		if err != nil {
 			log.Printf("SSH handshake err: %s", err)
 
-			handshakeAttempts += 1
+			// Only count this as an attempt if we were able to attempt
+			// to authenticate. Note this is very brittle since it depends
+			// on the string of the error... but I don't see any other way.
+			if strings.Contains(err.Error(), "authenticate") {
+				log.Printf("Detected authentication error. Increasing handshake attempts.")
+				handshakeAttempts += 1
+			}
+
 			if handshakeAttempts < 10 {
 				// Try to connect via SSH a handful of times
 				continue