Make passing Travis required for merge

[saad-ali]

Make passing Travis required for merge

xref kubernetes/test-infra#9014 (comment)

/assign @xing-yang

[xing-yang]

I have made "passing travis-ci required before merging". Let me know if anything is missing. Thanks!

[spiffxp]

@xing-yang you'll need to open a PR against https://github.com/kubernetes/test-infra/blob/master/prow/config.yaml for branch protection and required contexts to be enforced

eg for kubernetes/external-attacher: https://github.com/kubernetes/test-infra/blob/master/prow/config.yaml#L172-L175

[xing-yang]

Will do. Thanks!

[xing-yang]

PR submitted here: kubernetes/test-infra#9072

[xing-yang]

This is fixed now. Closing this issue.