Docs: Getting Started Guide for istio resulting in a broken example

[aslakknutsen]

What happened:
Following the Istio setup in the Getting Started Guide results in a non working setup (istio/istio#56055) as the two code bases have diverged.

What you expected to happen:
A working example.

How to reproduce it (as minimally and precisely as possible):
Using any "older" version of istio will trigger this bug as GIE has moved to not support BUFFERED processing mode.

Anything else we need to know?:

Environment:
*

Maybe some form of "testable docs" could be handy to catch regressions on both sides and as a light sanity check?

[nirrozenbaum]

@aslakknutsen can you add a link to the fix PR you created in Istio?
just to add more context for future readers of this issue.

[nirrozenbaum]

once that PR is merged in Istio, we should make sure Istio has a new tag with the fix and update our getting started guide accordingly.

CC @LiorLieberman @kfswain

[LiorLieberman]

Thanks! @nirrozenbaum lets keep this open until this is released.

For ref this is the PR that broke it - #672

[LiorLieberman]

/assign