PB-7173: Bug fix - Backup to not fail when there are non-PVC resources to be backed up

[kgarg-px]

What type of PR is this?

Uncomment only one and also add the corresponding label in the PR: bug

What this PR does / why we need it: Earlier when there were only non-PVC resources were present for the backup we were entering the loop backup.Status.Volumes) == backup.Status.FailedVolCount and failing the backup. Now the entry into this loop is changed and backup does not fail if only non-PVC resources are backed up

Does this PR change a user-facing CRD or CLI?:

Is a release note needed?:

Issue:
User Impact:
Resolution

Does this change need to be cherry-picked to a release branch?:

After the fix: As it can be seen in the screenshot, we have taken backup of only non-PVC resources and backup is successful.

Before this PR: