feat: Ensure that critical services have pod disruption budgets set

[alanmeadows]

http://kubernetes.io/docs/admin/disruptions/

This ensures that operators can safely drain nodes without having to understand all the complexity underneath.

Services that would require this and likely require "minAvailable:" would be:

• ceph monitors (2 for quorum)
• ceph osds (would think 2 but could be 1 since our default pool maintains 3 copies - this is understandably a simplification of more advanced configurations users may place on top such as pools with only 1 or 2 copies which would contradict this for now)
• mariadb (2 for quorum)
• All OpenStack API services: (1)
• DHCP and L3 services: (1)