cls_rgw: fix object name of objects removed on object creation

Fixes: #8972
Backport: firefly, dumpling

Reported-by: Patrycja Szabłowska <szablowska.patrycja@gmail.com>
Signed-off-by: Yehuda Sadeh <yehuda@redhat.com>
(cherry picked from commit 0f8929a68aed9bc3e50cf15765143a9c55826cd2)
rgw: fix crash in swift CORS preflight request

Fixes: #8586

This fixes error handling, in accordance with commit 6af5a537 that fixed
the same issue for the S3 case.

Signed-off-by: Yehuda Sadeh <yehuda@redhat.com>
(cherry picked from commit 18ea2a869791b4894f93fdafde140285f2e4fb65)