This change introduces some parameters to set up the service user token
feature for Barbican key manager, which was implemented during the Xena
cycle[1].
This basically replicates the implementation in puppet-keystone class.
We should not make this dependent on puppet-keystone to avoid circular
dependency between puppet-oslo and puppet-keystone.
[1] 162039467ad0dfc5e25a16b75d9072d607690702
Change-Id: I6d94318929cf4bcfc61180494110d0e5812356c0