Test jobs sometimes hang at cucumber report parsing step

We’ve noticed first time in test_Tails_ISO_feature-jessie #82 and test_Tails_ISO_stable #49 that test jobs sometimes hang at the cucumber report parsing step. It may be the first time it happens, it may be because we just tagged a lot of scenarios as @fragile and they are the first runs since then.

Parent Task: #5288 (closed)

Original created by @bertagaz on 10725 (Redmine)