http: fix agent.getName() and add tests

This commit fixes agent.getName(), which returned an extra colon
according to the docs, and adds tests (it was previously not unit
tested).

lib/_http_agent.js

@@ -107,7 +107,6 @@ Agent.prototype.getName = function(options) {
   name += ':';
   if (options.localAddress)
     name += options.localAddress;
-  name += ':';
   return name;
 };
 

test/parallel/test-http-agent-getname.js

@@ -0,0 +1,30 @@
+var assert = require('assert');
+var http = require('http');
+var common = require('../common');
+
+var agent = new http.Agent();
+
+// default to localhost
+assert.equal(
+  agent.getName({
+    port: 80,
+    localAddress: '192.168.1.1'
+  }),
+  'localhost:80:192.168.1.1'
+);
+
+// empty
+assert.equal(
+  agent.getName({}),
+  'localhost::'
+);
+
+// pass all arguments
+assert.equal(
+  agent.getName({
+    host: '0.0.0.0',
+    port: 80,
+    localAddress: '192.168.1.1'
+  }),
+  '0.0.0.0:80:192.168.1.1'
+);