OKD: fix entrypoint.sh for new SCOS builds

[bernhardloos]

Builds of OKD starting with 4.16 are based on CentOS Stream but the images identify as centos in /etc/os-release:

NAME="CentOS Stream"
VERSION="9"
ID="centos"
VERSION_ID="9"

See also okd-project/okd#2060

[openshift-ci]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: bernhardloos
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[openshift-ci]

Hi @bernhardloos. Thanks for your PR.

I'm waiting for a openshift member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[GingerGeek]

We are tracking this in OKD as okd-project/okd#2070