Added fix to wait if new instances of dataloader were declared during the processing

[OwlyCode]

This fix solves the awaitInstances method for cases like this :

$dataloader->load(1)->then(function () {
    $subLoader = new DataLoader(...);
    $subLoader->load(2);
});

Without the fix, awaitInstances() would stop on the first dataloader, ignoring the second one.

[coveralls]

Coverage decreased (-1.08%) to 98.925% when pulling 22dc047 on OwlyCode:wait-new-instances into 6cb2023 on overblog:master.

[coveralls]

Coverage remained the same at 100.0% when pulling 982077b2c35dd6870997254d3670161d776c76c8 on OwlyCode:wait-new-instances into 6cb2023 on overblog:master.

[coveralls]

Coverage remained the same at 100.0% when pulling 0fa6535 on OwlyCode:wait-new-instances into 6cb2023 on overblog:master.

[coveralls]

Coverage remained the same at 100.0% when pulling 0fa6535 on OwlyCode:wait-new-instances into 6cb2023 on overblog:master.

[mcg-web]

Thank you for the fix 👍