[heroes] Temporary mititgation for SACK

Hi all, Martin and me run the following command on "minnie" (the salt master):

minnie (saltmaster):~ # salt '*' cmd.run 'sysctl net.ipv4.tcp_sack=0' --out=text >/root/tcp_sack-fix.txt

This is a mitigation for the latest vulnerabilities in the TCP stack of Linux. Machines will still need to be updated and rebooted to properly (and persistently) fix the issue. Best regards, Karol Babioch