add comment field in istio.deps (#709)
add comment field in istio.deps (#709)

Automatic merge from submit-queue.

add comment field in istio.deps

This allows me to explain what istio.deps is used for. Having the field defined in the struct allows the comment to survive deserialization and serialization. 

This is safe even if the istio.deps does not have _comment defined.
istio/test-infra,istio/test-infra,istio/test-infra,istio/test-infra