BUG/MINOR: promex: create haproxy_backend_agg_server_status

haproxy_backend_agg_server_check_status currently aggregates
haproxy_server_status instead of haproxy_server_check_status.
We deprecate this and create a new one,
haproxy_backend_agg_server_status to clarify what it really
does.

This patch could be backported as far as 2.4.
3 files changed