Update submodule to `6efb8eb30e7025b168f3fda3ff83b9b386428ad6` (#1885)

* update submodule to `6efb8eb30e7025b168f3fda3ff83b9b386428ad6`
* unblock condition variable in `update_slots` when closing server

llm/ext_server/ext_server.cpp

@@ -111,6 +111,10 @@ void llama_server_stop() {
   // TODO - too verbose, remove once things are solid
   LOG_TEE("requesting llama server shutdown\n");
   ext_server_running = false;
+
+  // unblocks the update_slots() loop so it can clean up and exit
+  llama->request_cancel(0);
+
   ext_server_thread.join();
   delete llama;
   llama = NULL;

llama.cpp @ 6efb8eb3

-Subproject commit 328b83de23b33240e28f4e74900d1d06726f5eb1
+Subproject commit 6efb8eb30e7025b168f3fda3ff83b9b386428ad6