Implement VERIFY_NON_NULL() in terms VERIFY_NON_NULL_RET().

Implement VERIFY_NON_NULL() in terms VERIFY_NON_NULL_RET().

Minimize code duplication in the VERIFY_NON_NULL() macro by
implementing it terms of the VERIFY_NON_NULL_RET() macro.

Removed duplicate definitions of these macros as well.

Change-Id: I692b68744a0a1606ca64c7a676d910d32ffbbaf5
Signed-off-by: Ossama Othman <ossama.othman@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/1772
Reviewed-by: Jon A. Cruz <jonc@osg.samsung.com>
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Erich Keane <erich.keane@intel.com>