stream: be less eager with readable flag

As of 34b535f, test-child-process-flush-stdio was failing on CentOS 5 systems in CI due to the change in stream state checking in `child_process`. This commit fixes those failures by making readable streams less eager in setting their readable flag on EOF. Fixes: #4125 PR-URL: #4141 Reviewed-By: Colin Ihrig <[email protected]> Reviewed-By: James M Snell <[email protected]>

Author: mscdex

lib/_stream_readable.js

@@ -385,7 +385,6 @@ function onEofChunk(stream, state){
 }
 }
 state.ended=true;
-stream.readable=false;
 
 // emit 'readable' now to make sure it gets picked up.
 emitReadable(stream);