add zabbix-agent for essential monitoring for zabbix server

scripts/install

@@ -111,7 +111,7 @@ ar rcs zabbix-frontend-php+stretch_all-noapache2.deb debian-binary control.tar.g
 dpkg -i zabbix-frontend-php+stretch_all-noapache2.deb
 
 rm -fr zabbix-*.deb
-ynh_package_install zabbix-server-mysql
+ynh_package_install zabbix-server-mysql zabbix-agent
 DEBIAN_FRONTEND=noninteractive apt-mark hold zabbix-server-mysql zabbix-frontend-php
 
 sed -i "s/# fr_FR.UTF-8 UTF-8/fr_FR.UTF-8 UTF-8/g" /etc/locale.gen