fff0da8fe9
When a request going through Grafana data source proxy responds with a websocket
upgrade response we cannot override the response body since it produces an error.
This problem seems to have been introduced in Grafana v8.0 by #38962.
In addition #40303 added same problem.
Fixes #41292
(cherry picked from commit 3be452f995)
Co-authored-by: Marcus Efraimsson <marcus.efraimsson@gmail.com>