helm-charts avoiding autoinject

[jcchavezs]

Right now zipkin deployments by default avoid istio pod injection, while this is right or not we should be able to add some rationale to such behaviour.

https://github.com/openzipkin/zipkin/blob/master/charts/zipkin/values.yaml#L37

Ping @jonkerj @chirauki

[jonkerj]

I'm a bit divided on wether or not this default makes sense. On the one hand I think in a typical situation, Zipkin needs to be outside of the mesh (since you are debugging/tracing the mesh itself). This makes it usable for the first time users. On the other, if we leave the annotations dicts empty by default, it leaves a bit more freedom for the novices.

I tend to prefer the former (as it is our situation), but I agree it should be documented/explained in the README