icinga: Move NSCA code into module

- nsca::client does not seem to be used anywhere except the
  hadoop nodes
- the firewall rules misspelt NSCA as NCSA, corrected (I assume,
  since the port numbers match NSCA, and NCSA seems totally
  unrelated)

Change-Id: I4c6e84da376796253689a980a382ff62c8e29f56
Merge "icinga: Move NSCA code into module" into production