HAProxy: Make certmonger bundle the cert and key on renewal

HAProxy: Make certmonger bundle the cert and key on renewal

the postsave command is ran by certmonger when a certificate is
requested (which will happen on certificate renewal). The previous
command given didn't take into account the file that haproxy expects,
which is a bundled PEM file with both the certificate and the key. Thus,
certmonger would have never generated a new bundle that haproxy would
use, resulting in haproxy always having an old bundle after certificate
expiration.

This fixes that.

Change-Id: Idb650d35f56abaf6a17e17794a068dd5933e6a62
Closes-Bug: #1712514
(cherry picked from commit e1791a37d557b14bb8f833363cabe5c98e151548)