Traffic splitting not happening with App Mesh

`virtualservice` is set to split traffic 90% and 10% between two services, but invoking the `greeting` service returns response from only one of them.

@ geremyCohen will help with this.

No file or test is named; start by inspecting the App Mesh `virtualservice` and the `greeting` service configuration mentioned in the report, then reproduce requests against `greeting`. Done means the observed routing demonstrably follows the intended 90/10 split, or the discrepancy has a confirmed documented cause.

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