update URL for the libmnl to the official site

Summary: submitted by mchtech in https://github.com/facebookincubator/katran/pull/117

Reviewed By: sharmafb

Differential Revision: D27224983

fbshipit-source-id: f427f91a94ee35a48f66330e17cd56b4f9ce22c6

build/fbcode_builder/manifests/libmnl

@@ -9,7 +9,7 @@ libmnl-static
 libmnl-dev
 
 [download]
-url = http://www.lg.ps.pl/mirrors/ftp.netfilter.org/libmnl/libmnl-1.0.4.tar.bz2
+url = http://www.netfilter.org/pub/libmnl/libmnl-1.0.4.tar.bz2
 sha256 = 171f89699f286a5854b72b91d06e8f8e3683064c5901fb09d954a9ab6f551f81
 
 [build.os=linux]