Do not backup beta cluster deployment server

2b5e2d9c moved role::backup::host from the node to the role class
role::deployment::server. The later is applied on beta cluster
deployment host deployment-bastion which fails puppet due to bacula.

Harness the backup include for deployment server to prevent it from
being applied on labs.

Bug: T106003
Change-Id: I43c389364692171b34d4da89b4cc075cf9d2a147