Add ping util for post-install script
Logs during the install on very light debian :
Setting up ctparental (5.1.01-1.0) ...
/var/lib/dpkg/info/ctparental.postinst: 10: ping: not found
Logs during the install on very light debian :
Setting up ctparental (5.1.01-1.0) ...
/var/lib/dpkg/info/ctparental.postinst: 10: ping: not found