Added cosmetic change in etag field of CopyObjectResult (#388)

Problem: Observed discrepancy with AWS for CopyObject API's response. In MGW, "etag" field was not included in ("/ /")
Solution: Included etag field of CopyObject API's response in ("/ /") to make it AWS compliant 

Signed-off-by: shraddhaghatol <[email protected]>

Author: shraddhaghatol

src/rgw/rgw_rest_s3.cc

@@ -3330,7 +3330,7 @@ void RGWCopyObj_ObjStore_S3::send_response()
   if (op_ret == 0) {
     dump_time(s, "LastModified", mtime);
     if (!etag.empty()) {
-      s->formatter->dump_string("ETag", std::move(etag));
+      s->formatter->dump_format("ETag", "\"%s\"",etag.c_str());
     }
     s->formatter->close_section();
     rgw_flush_formatter_and_reset(s, s->formatter);