Add ignore unknown variables errors switch

Add ignore unknown variables errors switch to sysctl in
packstack puppet module neutron bridge manifest.

Change-Id: If7c0bb538bd0fa995e1fd6a72105d6415ae78ee5
Fixes: rhbz#1132129
(cherry picked from commit 16a766d81f2c525e95defa340949535826b26f82)
Merge "Add ignore unknown variables errors switch" into havana