ssh: add more logging when connecting with bastion

When a SSH bastion is used for connecting to a target, the operation is
done completely silently, making it hard to understand if it is working
as intended.

To make it easier to follow the path that the command is taking, we add
a few more INFO/DEBUG logs that parrot the actions it takes for
connecting.

communicator/step_connect_ssh.go

@@ -165,6 +165,8 @@ func (s *StepConnectSSH) waitForSSH(state multistep.StateBag, ctx context.Contex
 		var connFunc func() (net.Conn, error)
 		address := fmt.Sprintf("%s:%d", host, port)
 		if bAddr != "" {
+			log.Printf("[INFO] connecting with SSH to host %s through bastion at %s",
+				address, bAddr)
 			// We're using a bastion host, so use the bastion connfunc
 			connFunc = ssh.BastionConnectFunc(
 				bProto, bAddr, bConf, "tcp", address)

sdk-internals/communicator/ssh/connect.go

@@ -2,6 +2,7 @@ package ssh
 
 import (
 	"fmt"
+	"log"
 	"net"
 	"time"
 
@@ -62,6 +63,9 @@ func BastionConnectFunc(
 			return nil, fmt.Errorf("Error connecting to bastion: %s", err)
 		}
 
+		log.Println("[DEBUG] connected to bastion host")
+		log.Println("[DEBUG] attempting connection to destination host")
+
 		// Connect through to the end host
 		conn, err := bastion.Dial(proto, addr)
 		if err != nil {