Added sysctl -p in step 1 to activate changes in /etc/sysctl.conf in ubuntu

Change-Id: I8cd980e9b7be7b7e5a462976ff37b960fcbf8fd0
backport: havana
Closes-bug: #1250678
(cherry picked from commit e9ebd2a6e2615cd717f1884a4a73a80b7af59f4c)
Merge "Added sysctl -p in step 1 to activate changes in /etc/sysctl.conf in ubuntu" into stable/havana