Avoid using head when getting nodes

[mgencur]

Prevents errors such as:

 06:52:31.692 INFO:    Placing zipkin taint on first worker node
06:52:32.091 ERROR:   🚨 Error (code: 141) occurred at
./hack/lib/tracing.bash:19, with command: zipkin_node=$(oc get node -l
'node-role.kubernetes.io/worker' -oname | head -n 1)
06:52:32.093 ERROR:   Stack trace:
06:52:32.096 ERROR:    1: ./hack/lib/tracing.bash:6
dedicate_node_to_zipkin(...)
06:52:32.099 ERROR:    2: ./hack/tracing.sh:15 install_tracing(...)
make: *** [test-upgrade-with-mesh] Error 141

Fixes JIRA #

Proposed Changes

[cardil]

/lgtm

Thanks @mgencur

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cardil, mgencur

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[mgencur]

/hold

For upgrade tests to pass

[mgencur]

/unhold

[openshift-ci]

@mgencur: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/4.13-upstream-e2e-kafka-aws-ocp-413	5971987	link	false	/test 4.13-upstream-e2e-kafka-aws-ocp-413

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[dsimansk]

/cherry-pick release-1.30

[openshift-cherrypick-robot]

@dsimansk: new pull request created: #2286

In response to this:

/cherry-pick release-1.30

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