Cannot establish one or more browser connections when using concurrency mode

[felis2803]

When concurrent mode is used with more than 5 threads, TestCafe hangs and then throws an error:

Steps to reproduce:

1. Create a simple fixture with a few tests, for example:

fixture `New Fixture`
    .page `about:blank`;

for (let i = 0; i < 6; i++) {
    test(`test ${i}`, async t => {
        await t.expect(true).ok();
    });
}

2. Run using concurrent mode in 6 threads: testcafe browserstack:chrome -c 6 ./test.js You will get an error.
3. For comparison, run the same fixture in local chrome: testcafe chrome -c 6 ./test.js This should be successful.