client: Use string concatenation instead of Sprintf

Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>

client/ping.go

@@ -1,8 +1,6 @@
 package client
 
 import (
-	"fmt"
-
 	"github.com/docker/docker/api/types"
 	"golang.org/x/net/context"
 )
@@ -10,7 +8,7 @@ import (
 // Ping pings the server and returns the value of the "Docker-Experimental", "OS-Type" & "API-Version" headers
 func (cli *Client) Ping(ctx context.Context) (types.Ping, error) {
 	var ping types.Ping
-	req, err := cli.buildRequest("GET", fmt.Sprintf("%s/_ping", cli.basePath), nil, nil)
+	req, err := cli.buildRequest("GET", cli.basePath+"/_ping", nil, nil)
 	if err != nil {
 		return ping, err
 	}