Log format is incorrect in swift writer when etag and md5 are not equal

[ZhaoYixin]

Description
===========
When using the swift driver to put object in cinder-backup, when etag and md5 are not equal, the error log format is incorrect.

Expected result
===============
2020-11-21 06:58:19.254 15 ERROR cinder.backup.chunkeddriver [-] Invalid backup: error writing object to swift, MD5 of object in swift 01c4f20767d0466ce2bec1814676ce03 is not the same as MD5 of object sent to swift 1323c9a9af67a59178112f74e65036e1: InvalidBackup: Invalid backup: error writing object to swift, MD5 of object in swift 01c4f20767d0466ce2bec1814676ce03 is not the same as MD5 of object sent to swift 1323c9a9af67a59178112f74e65036e1

Actual result
=============
2020-11-21 06:58:19.254 15 ERROR cinder.backup.chunkeddriver [-] Invalid backup: (u'error writing object to swift, MD5 of object in swift %(etag)s is not the same as MD5 of object sent to swift %(md5)s', {'etag': '01c4f20767d0466ce2bec1814676ce03', 'md5': '1323c9a9af67a59178112f74e65036e1'}): InvalidBackup: Invalid backup: (u'error writing object to swift, MD5 of object in swift %(etag)s is not the same as MD5 of object sent to swift %(md5)s', {'etag': '01c4f20767d0466ce2bec1814676ce03', 'md5': '1323c9a9af67a59178112f74e65036e1'})

[michael-mcaleer (mmcaleer)]

Review: https://review.opendev.org/c/openstack/cinder/+/765304

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/cinder 18.0.0.0rc1 release candidate.