Fix spurious channel closures after meshlink_stop()+meshlink_start().

When restarting the mesh without fully closing the handle, channels should
continue to work MeshLink was only stopped briefly. However, we were
accidentily always setting the connection timeout when a node's UDP status
changed, which would cause channels that didn't have any unsent data to
time out.

diff --git a/src/utcp b/src/utcp
index 7baf55a28cf48163c007ee2ff56678371d78c990..ae9033c7c9211f6e9dfa3d6b3dfeebd6e1d9ba00 160000 (submodule)
--- a/src/utcp
+++ b/src/utcp
@@ -1 +1 @@
-Subproject commit 7baf55a28cf48163c007ee2ff56678371d78c990
+Subproject commit ae9033c7c9211f6e9dfa3d6b3dfeebd6e1d9ba00