integration tests run the istio galley validating admission webhook

[rosenhouse]

at startup, the test attempts to install an invalid VirtualService and checks that is rejected by the validator

ref:

• k8s admission controllers: https://kubernetes.io/docs/reference/access-authn-authz/admission-controllers/
• istio galley: https://github.com/istio/istio/tree/master/galley

#169304670

@tcdowney @rodolfo2488 @ndhanushkodi

[linux-foundation-easycla[bot]]

The committers are authorized under a signed CLA.

• :white_check_mark: Gabe Rosenhouse (dbbf16ffa4558723777f7906e228bcfe978498ce, 32412fb97f2f1e85997f9a2439625530b4d9d909)