ACQE-5700: fixed AdminAwsS3SyncZeroByteFilesTest for isolated run.

Author: jilu1

app/code/Magento/AwsS3/Test/Mftf/Test/AdminAwsS3SyncZeroByteFilesTest.xml

@@ -45,6 +45,10 @@
             <magentoCLI command="setup:config:set {{RemoteStorageAwsS3ConfigData.disable_options}}" stepKey="disableRemoteStorage"/>
         </after>
         <magentoCLI command="remote-storage:sync" timeout="200" stepKey="syncRemoteStorage"/>
-        <comment userInput="magentoCLI for remote-storage:sync must have been successful" stepKey="assertConfigTest"/>
+        <comment userInput="checking remote-storage:sync" stepKey="assertConfigTest"/>
+        <assertStringContainsString stepKey="checkingRemoteStorageSync">
+            <expectedResult type="string">Uploading media files to remote storage</expectedResult>
+            <actualResult type="variable">$syncRemoteStorage</actualResult>
+        </assertStringContainsString>
     </test>
 </tests>