Adding the master_lb_enabled option when creating a cluster,
which will benefit both the cloud provider side and the end
user side. For cloud prodiver, they don't have to maintain
separate cluster templates with or w/o master_lb_enabled enabled.
For end user, they can easily use one single template to create
different clusters with different configs.
Task: 39680
Story: 2007634
Change-Id: I0b586f05168ece84fd340ef7493a56688191053d
946c1d67c7