Set browser test concurrency to one

[daffl]

This is a first stab at getting the browser tests to run again. I've had similar problems in the Saucelabs browser tests of @feathersjs/client and throttling did help (it does use the Saucelabs provided Grunt task and tunnel though).

This PR may not pass since it doesn't have access to the Saucelabs environment variables but it is worth a try. Alternatives may be

• Use ngrok for localhost tunneling instead of localtunnel
• Use Grunt Saucelabs with the built in tunnel (this might require restructuring the tests a little)

[goto-bus-stop]

Oh rad, thanks! Trying it on a branch in the repository right now so it'll run the sauce tests. I think longer term we'll just be able to switch to airtap, a zuul fork that should be fixing most of zuul's problems soon.

[goto-bus-stop]

awesome, this just ran successfully twice in a row—i don't recall that ever happening before 😆 thanks a ton!

[daffl]

Awesome, glad it worked right away!