Make checkout.*.prepare() delete the svn:ignored files.

Add corresponding support to scm.SVN.Revert() to clobber the svn:ignore'd files.

This makes the commit queue remove all the unversioned files, which could have
improved its stability. It failed in practice to improve it but it's still a
good thing to do overall.

R=petermayo@chromium.org
BUG=
TEST=


Review URL: http://codereview.chromium.org/10355014

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@135333 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/checkout.py b/checkout.py
index 68b908c..6fb32d5 100644
--- a/checkout.py
+++ b/checkout.py
@@ -393,7 +393,7 @@
       self._check_call_svn(
           ['checkout', self.svn_url, self.project_path] + flags, cwd=None)
     else:
-      scm.SVN.Revert(self.project_path)
+      scm.SVN.Revert(self.project_path, no_ignore=True)
       # Revive files that were deleted in scm.SVN.Revert().
       self._check_call_svn(['update', '--force'] + flags)
     return self._get_revision()