Also don't fail if files are different and overwrite is false for uploads (this mimics copy and template).

Related to #489

lib/ansible/modules/cloud/amazon/s3.py

@@ -377,7 +377,7 @@ def main():
                 if overwrite is True:
                     download_s3file(module, s3, bucket, obj, dest)
                 else:
-                    module.exit_json(msg="WARNING: Checksums do not match. Use overwrite parameter to force download.", failed=False)
+                    module.exit_json(msg="WARNING: Checksums do not match. Use overwrite parameter to force download.")
 
         # Firstly, if key_matches is TRUE and overwrite is not enabled, we EXIT with a helpful message. 
         if sum_matches is True and overwrite is False:
@@ -421,7 +421,7 @@ def main():
                     if overwrite is True:
                         upload_s3file(module, s3, bucket, obj, src, expiry, metadata)
                     else:
-                        module.exit_json(msg="WARNING: Checksums do not match. Use overwrite parameter to force upload.", failed=True)
+                        module.exit_json(msg="WARNING: Checksums do not match. Use overwrite parameter to force upload.")
 
         # If neither exist (based on bucket existence), we can create both.
         if bucketrtn is False and pathrtn is True: