tests: Ensure that virtiofsd has exited before hotplugging

Fix test flakiness where the virtiofsd daemon was still running and
hotplugging was trying to reach the old version. Cleanup the socket so
that waiting for it actually waits for the new instance.

Signed-off-by: Rob Bradford <rbradford@meta.com>

cloud-hypervisor/tests/common/tests_wrappers.rs

@@ -1060,6 +1060,11 @@ pub(crate) fn _test_virtio_fs(
     });
 
     let (r, hotplug_daemon_child) = if r.is_ok() && hotplug {
+        let _ = daemon_child.kill();
+        let _ = daemon_child.wait();
+        // Remove the stale socket so wait_for_virtiofsd_socket actually waits
+        let _ = std::fs::remove_file(&virtiofsd_socket_path);
+
         let (daemon_child, virtiofsd_socket_path) =
             prepare_daemon(&guest.tmp_dir, shared_dir.to_str().unwrap());