storage: Upgrade REST version after adding WriteAll API (#6819)

Rolling update doesn't work properly because Storage REST API has
a new API WriteAll() but without API version number increase.

Also be sure to return 404 for unknown http paths.

cmd/storage-rest-common.go

@@ -16,7 +16,7 @@
 
 package cmd
 
-const storageRESTVersion = "v1"
+const storageRESTVersion = "v2"
 const storageRESTPath = minioReservedBucketPath + "/storage/" + storageRESTVersion + "/"
 
 const (

cmd/storage-rest-server.go

@@ -378,5 +378,6 @@ func registerStorageRESTHandlers(router *mux.Router, endpoints EndpointList) {
 		subrouter.Methods(http.MethodPost).Path("/" + storageRESTMethodRenameFile).HandlerFunc(httpTraceHdrs(server.RenameFileHandler)).
 			Queries(restQueries(storageRESTSrcVolume, storageRESTSrcPath, storageRESTDstVolume, storageRESTDstPath)...)
 
+		subrouter.NotFoundHandler = http.HandlerFunc(httpTraceAll(notFoundHandler))
 	}
 }