Update the update_iris_data.sh script

Use update_iris_data.sh to run download_snapshots.py.
Add set proxy feature, so that the script could download snapshots when we
need proxy.

Change-Id: Ib7303f591471c8df1a1f2af8c29397a73a199965
Signed-off-by: gaoxuesx <xuesongx.gao@intel.com>