remove libnl depedency from open source build
remove libnl depedency from open source build

Summary: We removed this dependency in the code a while ago.

Reviewed By: saifhhasan

Differential Revision: D18366401

fbshipit-source-id: daf1c7865fe0c312694bdf395f9d7ace99f70395

facebook/wangle,facebook/wangle,facebook/wangle