Add bootstrap label to all bootstrap containers to ensure that when
the a new container is launched a difference is seen between it and
the bootstrap container since we cannot rely on ENV variables for
this. This only affects mariadb at this stage, but it is needed to
ensure rabbitmq works when we switch to named volumes.

Change-Id: Ia022af26212d2e5445c06149848831037a508407
Closes-Bug: #1538136