contrib/jenkins: build nftables without python

We don't use the python bindings of nftables with osmo-upf, so don't
build them. Without this, it tries to build them with python2 for some
reason and since a recent nftables commit it fails with:

  running install
  Checking .pth file support in /build/deps/install/stow/nftables/lib/python2.7/site-packages/
  /usr/bin/python -E -c pass
  TEST FAILED: /build/deps/install/stow/nftables/lib/python2.7/site-packages/ does NOT support .pth files
  error: bad install directory or PYTHONPATH

Change-Id: Ie172dca3e6953c353239173bca07b1f62fbf4c34

contrib/jenkins.sh

@@ -50,7 +50,11 @@ build_from_netfilter() {
 	git clone "git://git.netfilter.org/$project" "$project"
 	cd "$project"
 	autoreconf --install --force
-	./configure --prefix="$inst/stow/$project" --without-cli --disable-man-doc
+	./configure \
+		--prefix="$inst/stow/$project" \
+		--without-cli \
+		--disable-man-doc \
+		--enable-python=no
 	$MAKE install
 	STOW_DIR="$inst/stow" stow --restow $project
 }