Fix downstream commit detection

[RadekManak]

In some cases, upstream commits were included in the git log command, causing the verify-git-history test to fail because the commits did not follow name rules.

[JoelSpeed]

Nice fix, this is happening a lot in various places, probably want to catch it up in a few places
CC @nrb you saw this recently I think
/lgtm
/approve

[openshift-ci]

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This pull-request has been approved by: JoelSpeed

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[nrb]

/retest

Timeouts seem to be flakes?

[openshift-ci]

@RadekManak: 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/e2e-vsphere-ovn	42fa4c2	link	false	/test e2e-vsphere-ovn

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