images/openstack: Make cli stage overrideable

[LorbusChris]

Analog to https://github.com/openshift/installer/blob/master/images/installer/Dockerfile.upi.ci#L11-L14

cc @vrutkovs

[LorbusChris]

(This is unrelated, I just want to get a second gcp e2e run for comparison)
/test e2e-gcp

[smarterclayton]

This shouldn't be necessary.

[LorbusChris]

this is a supposed fix for https://prow.svc.ci.openshift.org/view/gcs/origin-ci-test/pr-logs/pull/openshift_installer/2745/pull-ci-openshift-installer-master-e2e-openstack/3274#1:build-log.txt%3A74
which shouldn't have happened, but somehow did that one time.

[mandre]

/approve
It's not exactly clear to me how this is supposed to fix the above error (seems like a no-op change to me apart from the image version bump), however it does make the Dockerfile more consistent so 👍

[openshift-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: mandre

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[openshift-ci-robot]

@LorbusChris: The following tests failed, say /retest to rerun them all:

Test name	Commit	Details	Rerun command
ci/prow/e2e-gcp	17e5952	link	/test e2e-gcp
ci/prow/e2e-aws-scaleup-rhel7	b3db0ef	link	/test e2e-aws-scaleup-rhel7
ci/prow/e2e-libvirt	b3db0ef	link	/test e2e-libvirt

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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[pierreprinetti]

Thanks!
/lgtm