Fix ATH issues (hopefully)

- https://jenkins.ci.cloudbees.com/job/core/job/acceptance-test-harness/599/testReport/junit/plugins/NodeLabelParameterPluginTest/run_on_online_slave_and_master_with_node_restriction/
- https://jenkins.ci.cloudbees.com/job/core/job/acceptance-test-harness/599/testReport/junit/plugins/NodeLabelParameterPluginTest/run_on_several_slaves/