fixed and added a test for keepalive connection pool forced shutdown

test/fixtures/keepalive.js

@@ -0,0 +1,26 @@
+var elasticsearch = require('../../src/elasticsearch');
+var _ = require('lodash');
+var es = elasticsearch.Client({
+  host: 'localhost:5555',
+  log: false
+});
+
+es.search({
+  index: '_all',
+  type: '_all',
+  body: {
+    query: {
+      match_all: {}
+    }
+  }
+}, function (err, resp) {
+  var conn = _.union(es.transport.connectionPool._conns.dead, es.transport.connectionPool._conns.alive).pop();
+  es.close();
+  var destroyedSockets = 0;
+  function countDestroyed(sockets) {
+    destroyedSockets += _.where(sockets, { destroyed: true}).length;
+  }
+  _.each(conn.agent.sockets, countDestroyed);
+  _.each(conn.agent.freeSockets, countDestroyed);
+  console.log(destroyedSockets);
+});