fix: wrong npm doctor command result

Author: vanishcode

lib/doctor/check-ping.js

@@ -6,7 +6,7 @@ function checkPing (cb) {
  tracker.info('checkPing', 'Pinging registry')
  ping({}, true, (err, pong) => {
  if (err && err.code && err.code.match(/^E\d{3}$/)) {
- return cb(null, [err.code.substr(1)])
+ return cb(null, [err.code.substr(1), 'failed'])
  } else {
  cb(null, [200, 'ok'])
  }