Vivian/integration tests: make sure execution stops if the playbook fails

In a pre-merge, we ended up in a situation where the playbook failed to execute, but vivian kept on running nonetheless...

fatal: [vivian]: FAILED! => {"msg": "You need to install \"jmespath\" prior to running json_query filter"}
PLAY RECAP *********************************************************************
vivian                     : ok=49   changed=2    unreachable=0    failed=1    skipped=31   rescued=0    ignored=0   
make[2]: Leaving directory '/builds/mupuf/valve-infra'
[3332067.70]: Waiting for executor and vpdu

Let's get this fixed ASAP, as we may accidentally merge regressions.