Fixed issue with try where patchset is passed.

The new try execution should only be triggered when a user just passes the rietveld issue number. Usually, if your branch has a working patchset already defined, it shouldn't think the user passed it. The code has been updated to force patchset to be None (not 0 or any other number) so that specific occurence wont happen again.

TBR=maruel
BUG=None
TEST=git try, git try --issue=123, git try --issue=123 --patchset=0, should all work fine now.

Review URL: http://codereview.chromium.org/542007

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@35889 0039d316-1c4b-4281-b951-d872f2087c98

trychange.py

@@ -569,7 +569,7 @@ def TryChange(argv,
       if options.files:
         parser.error('You cannot specify files and --diff at the same time.')
       options.diff = gclient_utils.FileRead(options.diff, 'rb')
-    elif options.issue:
+    elif options.issue and options.patchset is None:
       # Retrieve the patch from rietveld when the diff is not specified.
       try:
         import simplejson