Try en even bigger sleep

test/640_proxy_restart_reattaches_test.sh

@@ -32,7 +32,7 @@ check_attached
 
 # Restart docker itself, using different commands for systemd- and upstart-managed.
 run_on $HOST1 sh -c "command -v systemctl >/dev/null && sudo systemctl restart docker || sudo service docker restart"
-sleep 5
+sleep 10
 check_attached
 
 # Restarting proxy shouldn't kill unattachable containers