[Streaming] Results from nodes with streaming set header X-Consul-Knownleader: false

When Streaming is running, the header `X-Consul-Knownleader: false` is set to false.

Some SDKs such as Orbitz, use this field to throw an error, thus, it fails to retrieve data.

This header should be set to true with streaming activated

No files or tests are named. Start by locating the streaming response handling and the code that sets X-Consul-Knownleader; reproduce a streaming request and verify that the header is true and affected SDKs can retrieve the data without an error.

Written by the indexing model from the issue text.