Previously we'd use two users, one admin and one unprivileged.
Ceph's s3-tests, however, assume that both users should have access to
create buckets. Further, there are different errors that may be returned
depending on whether you are the *bucket* owner or not when using
s3_acl. So now we've got:
test:tester1 (admin)
test:tester2 (also admin)
test:tester3 (unprivileged)
Change-Id: I0b67c53de3bcadc2c656d86131fca5f2c3114f14
5a8cfd6e06