Fix leaks by making sure no job is stalled

Summary:
Some tests leave a stalled job behind (generally composite ones with an
error in the middle) waiting for an event loop run in order to wrap
thing up and finally delete themselves. So make sure we run the event
loop before the test suite completes to collect those.

Reviewers: franckarrecot, dfaure, bensi

Differential Revision: https://phabricator.kde.org/D1286