Fix incorrect server packages

Nagios failed to install on Debian/Ubuntu.  Nagios should be Nagios3.  Found and confirmed via Test Kitchen
Clarify the new attribute for server and vname for icinga installs
Merge pull request #200 from tas50/master

[COOK-3729] - Update nagios plugins to the latest URL to fix broken RHEL NRPE installs
Drop TK memory allocation for clients from 1024 -> 512

Tested that this is still enough to compile the NRPE client.  No need to allocate more than that since some people only have dev systems with 4GB ram.
Add chef-zero to test kitchen, load data bags from test folder, reduce
memory to 512 on the test clients
Add chef-zero to the Gemfile