benchmark: allow zero when parsing http req/s

Without this, the http benchmarker would report "strange output" if
wrk or any other http client reported 0 requests per second, which is
a valid result.

PR-URL: https://github.com/nodejs/node/pull/10558
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>

benchmark/_http-benchmarkers.js

@@ -61,7 +61,7 @@ WrkBenchmarker.prototype.create = function(options) {
 WrkBenchmarker.prototype.processResults = function(output) {
   const match = output.match(this.regexp);
   const result = match && +match[1];
-  if (!result) {
+  if (!isFinite(result)) {
     return undefined;
   } else {
     return result;
@@ -126,7 +126,7 @@ exports.run = function(options, callback) {
     }
 
     const result = benchmarker.processResults(stdout);
-    if (!result) {
+    if (result === undefined) {
       callback(new Error(`${options.benchmarker} produced strange output: ` +
                          stdout, code));
       return;