remotedb/grpcdb: a net.Listener leaks if ListenAndServe's NewServer or srv.Serve errors in any way

[odeke-em]

If we examine the code in here

tm-db/remotedb/grpcdb/server.go

Lines 19 to 28 in b3c748f

	func ListenAndServe(addr, cert, key string, opts ...grpc.ServerOption) error {
	ln, err := net.Listen("tcp", addr)
	if err != nil {
	return err
	}
	srv, err := NewServer(cert, key, opts...)
	if err != nil {
	return err
	}
	return srv.Serve(ln)

we notice that after we invoke net.Listen there is a listener in there that'll be bound to an address, but if any error occurs it won't be released at all