Add proxy support

It's not possible to build the Docker images behind a corporate
proxy. This change adds support to HTTP and HTTPS protocols for
creation of images.

Change-Id: Iabe675d86e2879270dda069179b7b854da0a93bd
Signed-off-by: Victor Morales <victor.morales@intel.com>
diff --git a/sdc-os-chef/sdc-sanity/Dockerfile b/sdc-os-chef/sdc-sanity/Dockerfile
index dd48610..2b29131 100644
--- a/sdc-os-chef/sdc-sanity/Dockerfile
+++ b/sdc-os-chef/sdc-sanity/Dockerfile
@@ -1,4 +1,13 @@
 FROM ubuntu
+
+ARG HTTP_PROXY
+ARG HTTPS_PROXY
+
+ENV HTTP_PROXY  ${HTTP_PROXY}
+ENV HTTPS_PROXY ${HTTPS_PROXY}
+
+RUN if [ ! -z ${HTTP_PROXY} ]; then echo "Acquire::http::proxy  \"${HTTP_PROXY}\";" >> /etc/apt/apt.conf; fi && \
+    if [ ! -z ${HTTPS_PROXY} ]; then echo "Acquire::https::proxy \"${HTTPS_PROXY}\";" >> /etc/apt/apt.conf; fi 
 RUN apt-get -y update && apt-get -y install --no-install-recommends apt-utils
 RUN apt-get -y install curl
 RUN apt-get -y install vim