[telemetry] Exclude deleted files from Cloud Storage upload.

The PRESUBMIT automatically scans the CL for .sha1 files and syncs them to Cloud Storage. We should exclude deleted files.

BUG=None.
TEST=I don't know how to test this without actually messing up the repository or Cloud Storage :$
R=adamk@chromium.org, adamk, tonyg

Review URL: https://codereview.chromium.org/27770002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230065 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 230065