ds-querier: handle execute errors better (#105496)

* ds-querier: handle execute errors better

* fix: change how GetResponseCode works to return 418 if rsp is nil

418 is a bit of an easter egg which in this case works since we don't
have an rsp but we do know something went wrong, so a 200 won't work.

Also changed this to return the code in the frame, not sure why we
weren't.

* tests: fix GetResponseCode tests

* log no rsp case

* bring back og error log

pkg/apis/query/v0alpha1/query.go

@@ -31,11 +31,15 @@ type QueryDataResponse struct {
 // GetResponseCode return the right status code for the response by checking the responses.
 func GetResponseCode(rsp *backend.QueryDataResponse) int {
 	if rsp == nil {
-		return http.StatusBadRequest
+		return http.StatusTeapot // rsp is nil, so we return a teapot
 	}
 	for _, res := range rsp.Responses {
+		if res.Error != nil && res.Status != 0 {
+			return int(res.Status)
+		}
+
 		if res.Error != nil {
-			return http.StatusBadRequest
+			return http.StatusTeapot // Status is nil but we have an error, so we return a teapot
 		}
 	}
 	return http.StatusOK