Protractor throws errors on unknown commandline flags.

[krotscheck]

Bug report

Breaking change introduced by #3921 should be reverted.

Our project has implemented commandline flags (using yargs) that allow us to adjust the protractor.conf.js file to meet our environment needs. For example, we've implemented karma's --browsers flag to selectively filter our multiCapabilities list, so that devs can execute e2e tests against a specific browser without having to launch all the other ones.

• Node Version: 7.4
• Protractor Version: 5.0.0
• Angular Version: 2.2.4
• Browser(s): N/A
• Operating System and Version macOS Sierra
• Your protractor configuration file:

{
  ...,
  multiCapabilities: util.buildMultiCapabilities(args.browsers),
  ...
}

• A relevant example test

protractor --browsers=Safari-10,Safari-9.1

• Output from running the test

Error: Found extra flags: browsers
    at Object.<anonymous> (~/ui/node_modules/protractor/built/cli.js:172:15)
    at Module._compile (module.js:571:32)
    at Object.Module._extensions..js (module.js:580:10)
    at Module.load (module.js:488:32)
    at tryModuleLoad (module.js:447:12)
    at Function.Module._load (module.js:439:3)
    at Module.require (module.js:498:17)
    at require (internal/module.js:20:19)
    at Object.<anonymous> (~/ui/node_modules/protractor/bin/protractor:5:1)
    at Module._compile (module.js:571:32)

• Steps to reproduce the bug

1. Attempt to invoke protractor with a non-standard commandline flag or option.

[cnishina]

Please read the CHANGELOG. It says you should just send an additional flag --disableChecks