Add save_admin_pass property to CloudServer

This adds a save_admin_pass property to indicate whether or not the
admin_pass should be persisted in heat.  save_admin_pass is False by
default.

Implements: blueprint custom-adminpass (partial)
Change-Id: Iac59056abf2cf709ecb940b84c56d09fa3fbb7d4
Merge "Add save_admin_pass property to CloudServer"