This prevents the .test-container selector to appear twice in our test
markup:
```html
<div class="test-container passed" id="camunda-properties simple should
open stuff">
<div class="title-row">
<a href="#camunda-properties%20simple%20should%20open%20stuff">
<h3 class="test-titel">camunda-properties simple should open
stuff</h3>
</a>
<div class="test-result" style="float: right;">passed</div>
</div>
<div class="test-content-container test-container">
<!-- test content -->
</div>
</div>
```
With this commit we only add the .test-content-container marker in cases
where `mocha-test-container-support` is not present upon running
`bootstrapBpmnJS`.
c87167c8c6