[telemetry] Short circuit Cloud Storage upload check if no hash files.

Saves a few round trips, and skips any potential credentials errors.


BUG=None.
TEST=git cl presubmit

Review URL: https://codereview.chromium.org/180533002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253506 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 253506