Describe the bug

pkg/networking/plugin/mixer/mixer.go:           NetworkFailPolicy: &mccpb.NetworkFailPolicy{Policy: mccpb.FAIL_CLOSE},

A few folks I work with have Istio 1.0.x in production. They report seeing 503s anytime istio policy pod's health goes down. They would rather have fail open behavior than the current fail close behavior, but there is no way to configure this.

Expected behavior
Need a way to configure the failure mode to fail open through Helm.

Version
Istio 1.0.x

We need this in 1.0.x as well as 1.1..