Assorted bugs to get AU E2E test working with paygen suite.

1) Fixed a bug from a previous CL introduced that returned from an omaha
ping before we processed it for remote info (autoupdate.py)
2) If we expect a single item returned from gsutil but get multiple,
if the name we gave matches one exactly, return that.

BUG=chromium:267896
TEST=Ran it with unittests + AU E2E test with paygen test.

Change-Id: Ifd1266d9050824ad397df3bf80a1d314f01610db
Reviewed-on: https://gerrit.chromium.org/gerrit/66140
Tested-by: Chris Sosa <[email protected]>
Reviewed-by: Joy Chen <[email protected]>
Commit-Queue: Chris Sosa <[email protected]>
3 files changed