envoy: Disable http connection manager stream idle timeout.
envoy: Disable http connection manager stream idle timeout.

The default stream idle timeout functionality has been recently added
to Envoy with a default of 5 minutes. This interferes with HTTP long
polling and gRPC streaming, so disable the timeout by configuring it
as 0 (empty Duration message).

Signed-off-by: Jarno Rajahalme <0f1ab0ac7dffd9db21aa539af2fd4bb04abc3ad4@covalent.io>

scanf/cilium,michi-covalent/cilium,cilium/cilium,tgraf/cilium,tklauser/cilium,michi-covalent/cilium,cilium/cilium,tklauser/cilium,cilium/cilium,tgraf/cilium,michi-covalent/cilium,cilium/cilium,scanf/cilium,scanf/cilium,michi-covalent/cilium,tgraf/cilium,tklauser/cilium,tklauser/cilium,tklauser/cilium,scanf/cilium,tgraf/cilium,cilium-team/cilium,scanf/cilium,michi-covalent/cilium,cilium-team/cilium,cilium/cilium,tgraf/cilium,tgraf/cilium,scanf/cilium,scanf/cilium