MT#11063 Sync with bootenv: using deb.sipwise.com/wheezy-backports

At the moment we use wheezy-backports from repo 'wheezy-backports':
> http://debian.sipwise.com/wheezy-backports wheezy-backports main
which is actually not a Debain repository 'wheezy-backports',
but Sipwise repository 'wheezy-backports':
> http://deb.sipwise.com/wheezy-backports wheezy-backports main

It works currently because debian.sipwise.com and deb.sipwise.com are
the same host. So, we have to switch it to sync codebase with bootenv.git

Change-Id: I735402f3e077b5217f7bfa566b6fa7c0a3240a78

deployment.sh

@@ -183,7 +183,7 @@ fai_upgrade() {
   local TMPDIR=$(mktemp -d)
   mkdir -p "${TMPDIR}/statedir/lists/partial" "${TMPDIR}/cachedir/archives/partial"
   local debsrcfile=$(mktemp)
-  echo "deb http://${DEBIAN_REPO_HOST}/wheezy-backports wheezy-backports main" >> "$debsrcfile"
+  echo "deb http://${SIPWISE_REPO_HOST}/wheezy-backports wheezy-backports main" >> "$debsrcfile"
 
   DEBIAN_FRONTEND='noninteractive' apt-get -o dir::cache="${TMPDIR}/cachedir" \
     -o dir::state="${TMPDIR}/statedir" -o dir::etc::sourcelist="$debsrcfile" \