Remove duplicated rate_limit logs from HAProxy in ES

This is part of https://gitlab.com/gitlab-com/infrastructure/issues/2225

We currently have a decent amount of haproxy logs with the _grokparsefailures tag. They have duplicated information:

# not useful
Oct  6 15:56:15 fe08.lb.gitlab.com haproxy[24903]: Connect from 188.165.166.236:60246 to 10.65.1.108:443 (api_rate_limit/TCP)


# useful
Oct  6 15:56:15 fe08.lb.gitlab.com haproxy[24903]: 188.165.166.236:60246 [06/Oct/2017:15:56:15.142] https~ api_rate_limit/localhost 270/0/0/80/350 200 480 287 - - ---- 2819/1829/717/717/0 0/0 {Composer/1.2.1 (Linux; 4.1-dae-xen; PHP 5.5.25)} "GET /api/v3/projects/xxxx/repository/tags HTTP/1.1"

mentioned in merge request gitlab-cookbooks/gitlab-elk!78 (merged)

We've applied the changes, no more grok parse failures!