DAOS-17052 test: update expected msg for critical_integration

[daltonbohning]

Updated the expected journalctl message from "exited with 0" to "killed", since #15811 changed the default dmg system stop to use --force.

Skip-unit-tests: true
Skip-fault-injection-test: true

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[github-actions]

Ticket title is 'deployment/critical_integration.py:CriticalIntegrationWithServers.test_ras - Rank shut down message not found in journalctl'
Status is 'In Progress'
Labels: '2.6.3rc2,triaged,weekly_test'
https://daosio.atlassian.net/browse/DAOS-17052

[daosbuild1]

Test stage Functional Hardware Medium completed with status UNSTABLE. https://build.hpdd.intel.com/job/daos-stack/job/daos//view/change-requests/job/PR-15855/1/testReport/

[daltonbohning]

Tada! https://build.hpdd.intel.com/job/daos-stack/job/daos/job/PR-15855/2/testReport/FTEST_deployment/