Add mesh config to allow setting network policy fail open

[yangminzhu]

Cherrypick #670 to 1.0 branch.

istio/istio#9483, istio/istio#9485

[istio-testing]

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[mandarjog]

@yangminzhu please fix failed build. @douglas-reid does master and 1.0 use a different version of protoc / plugin?

[yangminzhu]

@mandarjog I think it's just I didn't include the generated file before.