System tests fail with request error

[JustinBeckwith]

This was getting masked by a problem with the logic in the system tests, which I'm about to fix. CI is failing for this here:
https://circleci.com/gh/googleapis/nodejs-translate/3384

It looks like this is related to the transition to teeny-request:

1) translate
       authentication
         should use an API key to authenticate:
     TypeError: Cannot read property 'defaults' of undefined
      at Util.makeRequest (node_modules/@google-cloud/common/src/util.ts:624:45)
      at Translate.request (src/index.ts:551:10)
      at Translate.getLanguages (src/index.ts:354:10)
      at Translate.wrapper (node_modules/@google-cloud/promisify/src/index.ts:73:29)
      at Context.it (system-test/translate.ts:165:17)

[fhinkel]

I see, we're trying to use config.request in common, but we set config.requestModule here.