http: unref socket timer on parser execute

When underlying `net.Socket` instance is consumed in http server - no
`data` events are emitted, and thus `socket.setTimeout` fires the
callback even if the data is constantly flowing into the socket.

Fix this by calling `socket._unrefTimer()` on every `onParserExecute`
call.

Fix: #5899
PR-URL: #6286
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/_http_server.js

@@ -364,6 +364,7 @@ function connectionListener(socket) {
   }
 
   function onParserExecute(ret, d) {
+    socket._unrefTimer();
     debug('SERVER socketOnParserExecute %d', ret);
     onParserExecuteCommon(ret, undefined);
   }

test/parallel/test-http-server-consumed-timeout.js

@@ -0,0 +1,36 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+const http = require('http');
+
+const server = http.createServer((req, res) => {
+  server.close();
+
+  res.writeHead(200);
+  res.flushHeaders();
+
+  req.setTimeout(common.platformTimeout(200), () => {
+    assert(false, 'Should not happen');
+  });
+  req.resume();
+  req.once('end', common.mustCall(() => {
+    res.end();
+  }));
+});
+
+server.listen(common.PORT, common.mustCall(() => {
+  const req = http.request({
+    port: common.PORT,
+    method: 'POST'
+  }, (res) => {
+    const interval = setInterval(() => {
+      req.write('a');
+    }, common.platformTimeout(25));
+    setTimeout(() => {
+      clearInterval(interval);
+      req.end();
+    }, common.platformTimeout(400));
+  });
+  req.write('.');
+}));