allow "members" property to be absent
allow "members" property to be absent

Closes-Bug: #1235904
Change-Id: If18f6d386d07ee65ce54f8372ad646864b486303
Signed-off-by: Stephen Gran <e847df4a1043ee59626fa7d2628adff5eb244acd@guardian.co.uk>

varunarya10/heat,rickerc/heat_audit,JioCloud/heat,rickerc/heat_audit,JioCloud/heat,varunarya10/heat