test: fix test-http-content-length

Previously the test did not allow the last request to complete.

Fixes: #1137
PR-URL: #1145
Reviewed-By: Brian White <[email protected]>
Reviewed-By: Bert Belder <[email protected]>

Author: Fishrock123

test/parallel/test-http-content-length.js

@@ -18,7 +18,7 @@ var expectedHeadersEndNoData = {
 };
 
 var receivedRequests = 0;
-var totalRequests = 2;
+var totalRequests = 3;
 
 var server = http.createServer(function(req, res) {
   res.removeHeader('Date');