test_backgroundparser: Fix assert in threadweaver

Problem:
FATAL : TestBackgroundparser::testShutdownWithRunningJobs() ASSERT
failure in virtual void ThreadWeaver::Weaver::finish_p(): "Suspending",
file /home/jenkins/sources/threadweaver/stable-kf5-qt5/src/weaver.cpp,
line 308
FAIL! : TestBackgroundparser::testShutdownWithRunningJobs() Received a
fatal error.

Loc: [Unknown file(0)]