ResellerAdmin role is used to give users object storage administration role
in their projects.

It is required to pass object storage quotas tests[1] of DefCore (OpenStack
Powered) certification test suite.

[1] tempest.api.object_storage.test_account_quotas*
Related-Bug: #1700729

Change-Id: Id976827aa7da271e54b77476f175f06bd1a00cc8