Make token mapping non-blocking in the overlapped mode (#1740)

test/killall_sglang.sh

@@ -1 +1,2 @@
 kill -9 $(ps aux | grep 'multiprocessing.spawn' | grep -v 'grep' | awk '{print $2}')
+kill -9 $(ps aux | grep 'sglang.launch_server' | grep -v 'grep' | awk '{print $2}')