Re-enable Cereal download

Re-enable Cereal download

The build post-CA/Master merge seems to have lost the auto-download
functionality that we put in to allow cereal to be captured
automatically.

This fix re-enables the script, which should fix a few of the
other build servers listening in.

Change-Id: Icf3d0d0ed0babaef37f2ceace55abc471a73d306
Signed-off-by: Erich Keane <erich.keane@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/693
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Vijay Kesavan <vijay.s.kesavan@intel.com>
Reviewed-by: Uze Choi <uzchoi@samsung.com>
Reviewed-by: Jihun Ha <jihun.ha@samsung.com>