Call SetDirectory in OAuth TLS Config (#337)

Signed-off-by: Julien Pivotto <roidelapluie@inuits.eu>
diff --git a/config/http_config.go b/config/http_config.go
index 5f520ed..4b87241 100644
--- a/config/http_config.go
+++ b/config/http_config.go
@@ -170,6 +170,7 @@
 		return
 	}
 	a.ClientSecretFile = JoinDir(dir, a.ClientSecretFile)
+	a.TLSConfig.SetDirectory(dir)
 }
 
 // HTTPClientConfig configures an HTTP client.