allow requests to be proxied when server is booting up (#10790)

when server is booting up there is a possibility
that users might see '503' because object layer
when not initialized, then the request is proxied
to neighboring peers first one which is online.

cmd/routers.go

@@ -39,6 +39,10 @@ func registerDistErasureRouters(router *mux.Router, endpointServerSets EndpointS
 
 // List of some generic handlers which are applied for all incoming requests.
 var globalHandlers = []MiddlewareFunc{
+	// add redirect handler to redirect
+	// requests when object layer is not
+	// initialized.
+	setRedirectHandler,
 	// set x-amz-request-id header.
 	addCustomHeaders,
 	// set HTTP security headers such as Content-Security-Policy.