[IAP]Change the git url of marketbilling repo

As google code hasn't held the source code, and the marketbilling codes
have been exported to github, so update the url of the repo to
https://github.com/marchbold/marketbilling.git

BUG=

iap/ensure_iab_helper.py

@@ -50,7 +50,7 @@ def EnsureAndEnterIABRepo(output_dir, repo):
 
   repo_dir = os.path.join(output_dir, repo)
 
-  git_url = 'https://code.google.com/p/%s/' % repo
+  git_url = 'https://github.com/marchbold/marketbilling.git'
   co = GitCheckout(repo_dir, None, 'master', git_url, None)
   co.prepare('ff1c062b22b97c3baee12eae8d65a2adcf396f5f')