chunker: skip norename overwrite tests on remotes without metadata

The server-side overwrite tests ran norename transactions on the
nometa test remotes, which can't support them, so they failed with
"readXactID requires valid metaobject".

backend/chunker/chunker_internal_test.go

@@ -928,6 +928,9 @@ func testChunkerServerSideOverwrite(t *testing.T, moveFs *Fs) {
 			for _, transactionMode := range transactionModes {
 				t.Run(transactionMode.name, func(t *testing.T) {
 					f := operation.fs
+					if transactionMode.useNoRename && !f.useMeta {
+						t.Skip("Can't test norename transactions without metadata")
+					}
 					oldUseNoRename := f.useNoRename
 					f.useNoRename = transactionMode.useNoRename
 					defer func() { f.useNoRename = oldUseNoRename }()