Replace @example.com in OpenStack service users

The fix for bug 1362173 replaced @mirantis.com addresses
with @example.com addresses. Those should have been
replaced with @localhost addresses in order to maintain
consistency with other services address, as well as
preventing the services from potentially spamming
@example.com.

Change-Id: Ib10d64317ae162b00288630b37f57576490a5939