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 <sosa@chromium.org>
Reviewed-by: Joy Chen <joychen@chromium.org>
Commit-Queue: Chris Sosa <sosa@chromium.org>
diff --git a/build_artifact.py b/build_artifact.py
index d55e6c4..432c4b2 100755
--- a/build_artifact.py
+++ b/build_artifact.py
@@ -185,6 +185,9 @@
     return '->'.join(['%s/%s' % (self.archive_url, self.name),
                      self.install_dir])
 
+  def __repr__(self):
+    return str(self)
+
 
 class AUTestPayloadBuildArtifact(BuildArtifact):
   """Wrapper for AUTest delta payloads which need additional setup."""