raddb: Move trigger.conf INCLUDE before modules

Move "$INCLUDE trigger.conf" chunk before module section in
"radiusd.conf.in". This makes it possible to reference "snmptrap" and
related trigger variables under "pool.trigger" in module configurations,
simplifying them.

E.g. like this (in raddb/mods-enabled/ldap):

ldap ldap_instance {
    pool {
        trigger {
            args = "radiusdModuleName s '${...:name}' radiusdModuleInstance s '${...:instance}'"
            open = "${snmptrap}::serverModuleConnectionUp ${args}"
            close = "${snmptrap}::serverModuleConnectionDown ${args}"
        }
    }
}
Merge pull request #857 from spbnick/move_trigger_include

raddb: Move trigger.conf INCLUDE before modules