Use sysctl -p instead of --load

The --load option is in newer sysctl only (3.3 or newer).

Instead of using it lets just use the old -p option instead.

This should help TripleO CI to pass when using precise...

Change-Id: Iea8fa94c1c29abab0fe3b3c9268b29e6f6e86318
Merge "Use sysctl -p instead of --load"