Pass role=1 as the concurrency argument for each role.

This allows generation of upstart scripts for only the foreman processes for which a role is passed on each server.

The following example:

role :app, server1.example.com, server2.example.com
role :worker, server1.example.com

Will generate `-c app=1,worker=1` for server1 and `-c app=1` for server2.