s3api: fix TestRoutedMultipartFinalize flake from a reused fake filer port (#12571)

* s3api: drop cached gRPC channels when a fake filer takes a port

A test that dials a dead owner leaves its failed channel in the
process-wide gRPC connection cache. When a later test's fake filer is
given the same port, its first RPC fails at once with the cached
connection refused, which is how TestRoutedMultipartFinalize failed on
the 32-bit job. The fake filer helpers now share fakeFilerAddress, which
invalidates any cached channel for the new address.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* s3api: test a fake filer on a dead owner's reused port

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* s3api: drop cached channels for dead test filer addresses too

closedFilerAddress can be handed a port whose cached channel belonged to
a fake filer that just stopped and may still look ready; then the dead
owner's transaction is sent on it instead of failing over. Build its
address with fakeFilerAddress as well.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

weed/s3api/s3api_remote_storage_test.go

@@ -537,8 +537,7 @@ func startFakeCacheFiler(t *testing.T, impl *fakeCacheFiler) pb.ServerAddress {
 	filer_pb.RegisterSeaweedFilerServer(srv, impl)
 	go srv.Serve(lis)
 	t.Cleanup(srv.Stop)
-	port := lis.Addr().(*net.TCPAddr).Port
-	return pb.ServerAddress(fmt.Sprintf("127.0.0.1:1.%d", port))
+	return fakeFilerAddress(lis)
 }
 
 func newRemoteCacheTestServer(filerAddr pb.ServerAddress) *S3ApiServer {