This PR adds /api/gnet to the list of ignored paths in the gzip middleware.
Without this, when gzip is enabled (`server.enable_gzip = true`), responses
from the gnet proxy are double compressed: once by grafana.com and once by
Grafana itself. With this change we only do one round of compression for these
endpoints.
To test this out, try a request like this with `server.enable_gzip = true`
(after setting `GCOM_TOKEN` to a valid grafana.com token; you may need to
change the 'bsull' slug, too):
curl -v --user admin:admin \
-H "X-Api-Key: $GCOM_TOKEN" \
-H 'Accept-Encoding: gzip' \
localhost:3000/api/gnet/instances/bsull/provisioned-plugins/grafana-ml-app | gzip -d
Note that there are two Content-Encoding: gzip headers before this PR, and
the output is still compressed even after the `gzip -d`. After this PR things
look as expected.
