Fix Docker daemon wait

Also, a few various cleanups are bundled:

1. Only call GetDriver() once to get the object in provision/utils.go
2. SSH command wrapper will return the error and let the consumer decide
   what to do with it instead of bailing automatically on non-255

Signed-off-by: Nathan LeClaire <nathan.leclaire@gmail.com>

libmachine/ssh/ssh.go

@@ -1,22 +0,0 @@
-package ssh
-
-import (
-	"net"
-	"time"
-
-	"github.com/docker/machine/libmachine/log"
-)
-
-func WaitForTCP(addr string) error {
-	for {
-		log.Debugf("Testing TCP connection to: %s", addr)
-		conn, err := net.DialTimeout("tcp", addr, 2*time.Second)
-
-		if err != nil {
-			continue
-		}
-
-		defer conn.Close()
-		return nil
-	}
-}