fix token refresh for GKE on Windows

A proper solution would be to pass command line arguments as an array.
Unfortunately, this is not currently possible with shelljs. See also
shelljs/shelljs#143.

As a workaround, surround the command with quotes to at least fix
commands with spaces.

Closes #50.

node-client/src/config.ts

@@ -130,7 +130,7 @@ export class KubeConfig {
                 let expiration = Date.parse(expiry);
                 if (expiration < Date.now()) {
                     if (config['cmd-path']) {
-                        let cmd = config['cmd-path'];
+                        let cmd = '"' + config['cmd-path'] + '"';
                         if (config['cmd-args']) {
                             cmd = cmd + ' ' + config['cmd-args'];
                         }