Currently this is only affecting cellular AU delta tests

Here is an example update_engine log 

[1104/125550:INFO:omaha_request_action.cc(1210)] Omaha request response: 
          <response protocol="3.0">
            <daystart elapsed_seconds="44801"/>
              <app appid="{85F8FA82-F276-4EA6-8980-93FE091F6D25}" status="ok">
              <ping status="ok"/>
                <updatecheck status="ok">
                <urls>
                  <url codebase="https://storage.googleapis.com/"/><url codebase="https://storage.googleapis.com/"/>
                </urls>
                <manifest version="999999.0.0">
                  <packages>
                    <package hash_sha256="e3b1870e090dfce08de35b47df9768c48f5740e84f58485c8367b64b7e651145" name="chromeos-throw-away-bucket/CrOSPayloads/Cellular/chromeos_R72-11226.0.0_R72-11226.0.0_nautilus_delta_dev.bin"
                    size="239285" required="true"/>
                  </packages>
                  <actions>
                    <action event="postinstall"
                    ChromeOSVersion="999999.0.0"
                    sha256="e3b1870e090dfce08de35b47df9768c48f5740e84f58485c8367b64b7e651145"
                    needsadmin="false"
                    IsDeltaPayload="true"
                    MaxFailureCountPerUrl="1"
                    DisablePayloadBackoff="true"
                    IsDeltaPayload="true"
                    deadline="now"
                    />
                  </actions>
                </manifest>
              </updatecheck>
            </app>
          </response>
        
[1104/125550:INFO:omaha_request_action.cc(1899)] No device policy is loaded. Assuming rollback enabled.
[1104/125550:INFO:omaha_request_action.cc(1929)] Rollback is enabled. Setting kernel_max_rollforward to 65537
[1104/125552:INFO:metrics_reporter_omaha.cc(609)] Sending 65537 for metric UpdateEngine.KernelKey.MinVersion
[1104/125552:INFO:metrics_reporter_omaha.cc(614)] Sending 65537 for metric UpdateEngine.KernelKey.MaxRollforwardVersion
[1104/125552:INFO:metrics_reporter_omaha.cc(619)] Sending 1 for metric UpdateEngine.KernelKey.MaxRollforwardSetSuccess (bool)
[1104/125552:ERROR:omaha_request_action.cc(1248)] Omaha response not valid XML: duplicate attribute at line 23 col 20
[