http: tiny fix in http.js

Fixes #1885.

lib/http.js

@@ -956,8 +956,11 @@ Agent.prototype.createSocket = function(name, host, port) {
   return s;
 };
 Agent.prototype.removeSocket = function(s, name, host, port) {
-  if (this.sockets[name] && this.sockets[name].indexOf(s) !== -1) {
+  if (this.sockets[name]) {
-    this.sockets[name].shift(this.sockets[name].indexOf(s));
+    var index = this.sockets[name].indexOf(s);
+    if (index !== -1) {
+      this.sockets[name].splice(index, 1);
+    }
   } else if (this.sockets[name] && this.sockets[name].length === 0) {
     // don't leak
     delete this.sockets[name];