Disable istio sidecar injection in simple tfjob test

[Bobgy]

Unblocks kubeflow/kfctl#131, because kfctl uses tf-operator head for presubmit test.
After enabling istio sidecar injection in kubeflow namespace, tfjob-smoke-test is the only test timing out.

I haven't been able to look at pod log/info because there were permission issues, but I've found other people mentioning tfjob cannot work with istio sidecar: kubeflow/kubeflow#3935

/cc @jlewi

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This change is 

[Bobgy]

/assign @richardsliu

[gaocegege]

/lgtm

[Bobgy]

/cc @jlewi

[coveralls]

Coverage remained the same at 96.512% when pulling 2c4afd4 on Bobgy:patch-1 into 8048775 on kubeflow:master.

[Bobgy]

Looks like a flaky test.
/retest

[Bobgy]

Tests are passing now.
@gaocegege @richardsliu Any concerns? Can you approve?

[jlewi]

/lgtm
/approve

[ChanYiLin]

@gaocegege @richardsliu
do you think we should disable istio injection for all tf-operator job?
I wonder will istio affect the communication between components of tfjob (ps, workers).
we can probably open an issue and discussed there

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ChanYiLin, jlewi

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[Bobgy]

Thank you @ChanYiLin!