Datasource: Make sure data proxy timeout applies to HTTP client (#25865)

For backend data sources executing in the backend (not through data proxy) make 
sure that the timeout applies to cached HTTP client.

Fixes #25863

Co-authored-by: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>

pkg/models/datasource_cache.go

@@ -51,7 +51,7 @@ func (ds *DataSource) GetHttpClient() (*http.Client, error) {
 	}
 
 	return &http.Client{
-		Timeout:   30 * time.Second,
+		Timeout:   time.Duration(setting.DataProxyTimeout) * time.Second,
 		Transport: transport,
 	}, nil
 }