ts.fetch() stops working in ts_lua plugin

The fetch functionality of the ts_lua plugin stops working. More specifically the example here -(https://github.com/apache/trafficserver/blob/master/plugins/experimental/ts_lua/example/test_fetch.lua) stops working and results in the request being hanged without finishing.

The traffic.out/ squid.log shows that the fetch is finished successfully but main transaction somehow is not getting reenabled.

Furthermore, this works fine before the fix of TS-3777. The introduction of the code to disable keep-alive for internal transaction is causing this.