Fix uv_loop_close sequence to wait for in-flight synchronous calls that hold uv resources

src/host/run.cpp

@@ -1018,21 +1018,22 @@ namespace ccf
 
     process_launcher.stop();
 
-    // Continue running the loop long enough for the on_close
-    // callbacks to be despatched, so as to avoid memory being
-    // leaked by handles. Capped out of abundance of caution.
-    constexpr size_t max_iterations = 1000;
-    size_t close_iterations = max_iterations;
-    while ((uv_loop_alive(uv_default_loop()) != 0) && (close_iterations > 0))
+    constexpr size_t max_close_iterations = 1000;
+    int close_iterations = max_close_iterations;
+    int loop_close_rc = 0;
+    while (close_iterations-- > 0)
     {
+      loop_close_rc = uv_loop_close(uv_default_loop());
+      if (loop_close_rc != UV_EBUSY)
+      {
+        break;
+      }
       uv_run(uv_default_loop(), UV_RUN_NOWAIT);
-      close_iterations--;
+      std::this_thread::sleep_for(10ms);
     }
     LOG_INFO_FMT(
       "Ran an extra {} cleanup iteration(s)",
-      max_iterations - close_iterations);
-
-    auto loop_close_rc = uv_loop_close(uv_default_loop());
+      max_close_iterations - close_iterations);
     if (loop_close_rc != 0)
     {
       LOG_FAIL_FMT(