Fix failing build

[edescourtis]

  1 failing
  1) Resolve servers timeout exceeded total failure "before all" hook:
     Error: Invalid arguments: argument should be a boolean
      at Scope.persist (/home/travis/build/resilient-http/resilient.js/node_modules/nock/lib/scope.js:208:11)
      at context.<anonymous> (/home/travis/build/resilient-http/resilient.js/test/resolve-servers.js:74:10)
      at callFn (/home/travis/build/resilient-http/resilient.js/node_modules/mocha/lib/runnable.js:250:21)
      at Hook.Runnable.run (/home/travis/build/resilient-http/resilient.js/node_modules/mocha/lib/runnable.js:243:7)
      at next (/home/travis/build/resilient-http/resilient.js/node_modules/mocha/lib/runner.js:258:10)
      at Immediate.<anonymous> (/home/travis/build/resilient-http/resilient.js/node_modules/mocha/lib/runner.js:275:5)
      at runCallback (timers.js:693:18)
      at tryOnImmediate (timers.js:664:5)
      at processImmediate (timers.js:646:5)