CFE-882: add few test cases for external-certificate

[chiragkyal]

Follow up : #1625

[openshift-ci-robot]

@chiragkyal: This pull request references CFE-882 which is a valid jira issue.

Warning: The referenced jira issue has an invalid target version for the target branch this PR targets: expected the sub-task to target the "4.16.0" version, but no target version was set.

In response to this:

Follow up : #1625

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[chiragkyal]

/assign @alebedev87 @Miciah

[openshift-ci]

@chiragkyal: all tests passed!

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[Miciah]

/approve
/lgtm
Thanks!
/hold
in case @alebedev87 wants to review.

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: chiragkyal, Miciah

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[alebedev87]

/unhold