client.ContainerWait(): don't send empty "condition" query parameter

The client would always send a value, even if no `condition` was set;

    Calling POST /v1.41/containers/foo/wait?condition=

This patch changes the client to not send the parameter if it's empty (and the
API default value should be used).

Signed-off-by: Sebastiaan van Stijn <[email protected]>

client/container_wait.go

@@ -33,7 +33,9 @@ func (cli *Client) ContainerWait(ctx context.Context, containerID string, condit
 	errC := make(chan error, 1)
 
 	query := url.Values{}
-	query.Set("condition", string(condition))
+	if condition != "" {
+		query.Set("condition", string(condition))
+	}
 
 	resp, err := cli.post(ctx, "/containers/"+containerID+"/wait", query, nil, nil)
 	if err != nil {