Update check-haproxy.rb
Update check-haproxy.rb

Extended sessions warning and critical output to also show sessions limit.

Old output:
`CheckHAProxy CRITICAL: UP: 100% of 10 // services; Active sessions critical: 10684 web.BACKEND`

New output:
`CheckHAProxy CRITICAL: UP: 100% of 10 // services; Active sessions critical: 10684 of 15000 web.BACKEND`
sensu-plugins/sensu-plugins-haproxy