e2e: fix two_clusters.go if there are multiple users under ROOT/admin

[weizhouapache]

Issue #, if available:

When there are multiple users under account ROOT/admin, the e2e test two_clusters.go fails with error
"could not find sufficient user (with API keys) in domain/account ROOT/admin"

Description of changes:

The issue is fixed by setting the user ID if it exists.

Testing performed:

The following test passes

JOB='"should successfully add and remove a second cluster without breaking the first cluster"' make run-e2e 

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[k8s-ci-robot]

Hi @weizhouapache. Thanks for your PR.

I'm waiting for a kubernetes-sigs 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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Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[rohityadavcloud]

/ok-to-test

[rohityadavcloud]

/approve

[rohityadavcloud]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: rohityadavcloud, weizhouapache

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[rohityadavcloud]

/lgtm