MCG Scale tests might wait over or under the needed time when deleting S3 buckets

[sagihirshfeld]

In #11511 we've noticed that we sometimes wait exactly 30 minutes between the deletion of objects from an MCG S3 bucket to the deletion of the bucket, if the scale mark was used for the test: https://github.com/red-hat-storage/ocs-ci/blob/master/ocs_ci/ocs/resources/objectbucket.py/#L489-L490

This hardcoded approach is likely to result in higher wait time than needed, and sometimes might not be enough.
We need to replace this with a dynamic solution using TimeoutSampler or retry.