Install multiple agents on a node.

- node[:go][:agent][:instance_count] controls how many agents get installed on a node.  Default is one per CPU.

This cookbook now replaces the init.d service and helper scripts that come in the Go debian package with versions from the cookbook.  The cookbook versions are based on Go 13.2.0 and used as templates.

A single Go agent binary is installed, but multiple runtime directories are used.

/var/lib/go-agent[-n] 

Tested on Ubuntu 12.04 LTS.  /etc/defaults/go-agent-* likely needs updating for anything beyond Ubuntu.  What's the proper way to find JAVA_HOME?!