restore lost curl for netplugin release tarball

Curl went missing with this commit:

dbe1988#diff-d99b26f864526f6f8f79861d49deb922L149

Signed-off-by: Chris Plock <chrisplo@cisco.com>

scripts/build.sh

@@ -146,6 +146,7 @@ docker save $aci_image -o $binary_cache/aci-gw-image.tar
 curl --fail -sL -o $binary_cache/openvswitch-2.5.0-2.el7.x86_64.rpm http://cbs.centos.org/kojifiles/packages/openvswitch/2.5.0/2.el7/x86_64/openvswitch-2.5.0-2.el7.x86_64.rpm
 curl --fail -sL -o $binary_cache/ovs-common.deb http://mirrors.kernel.org/ubuntu/pool/main/o/openvswitch/openvswitch-common_2.5.2-0ubuntu0.16.04.3_amd64.deb
 curl --fail -sL -o $binary_cache/ovs-switch.deb http://mirrors.kernel.org/ubuntu/pool/main/o/openvswitch/openvswitch-switch_2.5.2-0ubuntu0.16.04.3_amd64.deb
+curl --fail -sL -o $binary_cache/netplugin-$contiv_version.tar.bz2 https://github.com/contiv/netplugin/releases/download/$contiv_version/netplugin-$contiv_version.tar.bz2
 
 env_file=$output_dir/install/ansible/env.json
 sed -i.bak 's#__AUTH_PROXY_LOCAL_INSTALL__#true#g' "$env_file"