Added RedHat os_family support for zabbix 2.2 from epel

Hello!
We extended zabbix-formula for RedHat os_family. We use it with CentOS 6.5.
1. Added support for RedHat in map.jinja
2. Changed zabbix_agentd.conf.jinja to have "Include=" only when it is defined in pillar.
By default zabbix22 from epel does not have include directory and it must be created/configured by user.

Thanks!