Fix gcl.py error introduced in r196786.

The hostname was used instead of the rpc object.

TBR=phajdan.jr@chromium.org
BUG=

Review URL: https://chromiumcodereview.appspot.com/14305019

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@196798 0039d316-1c4b-4281-b951-d872f2087c98

gcl.py

@@ -389,7 +389,7 @@ class ChangeInfo(object):
   def GetApprovingReviewers(self):
     """Returns the issue reviewers list from Rietveld."""
     return git_cl.get_approving_reviewers(
-        self.rietveld.get_issue_properties(self.issue, False))
+        self.RpcServer().get_issue_properties(self.issue, False))
 
   def AddComment(self, comment):
     """Adds a comment for an issue on Rietveld.