Use "http://chromegw/i/tryserver.chromiumos/" for retrieving builder info.

This "/i/" url is the internal version of
"http://chromegw/p/tryserver.chromiumos/". And "/i/" links offer
waterfall controls (force build, stop build, etc.) and work for both
internal and public waterfalls, whereas "/p/" links only work for
public waterfalls.

BUG=None
TEST=buildbot_json.py works well with this url.

Change-Id: I55bebdb53020447156df2f7477dd3d9a32478660
Reviewed-on: https://chrome-internal-review.googlesource.com/214840
Reviewed-by: Caroline Tice <cmtice@google.com>
Commit-Queue: Han Shen <shenhan@google.com>
Tested-by: Han Shen <shenhan@google.com>
diff --git a/utils/buildbot_utils.py b/utils/buildbot_utils.py
index 8f0f35d..cc93291 100644
--- a/utils/buildbot_utils.py
+++ b/utils/buildbot_utils.py
@@ -108,7 +108,7 @@
     """
     ce = command_executer.GetCommandExecuter()
     commands = ("{0}/utils/buildbot_json.py builds "
-                "http://chromegw/p/tryserver.chromiumos/"
+                "http://chromegw/i/tryserver.chromiumos/"
                 .format(file_dir))
 
     _, buildinfo, _ = ce.RunCommand(commands, return_output=True,