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.
(cherry picked from commit 946c1d67c73a1b325dadd27018c38555acfee52f)