Fix default value field serializer for marketplace offering options.
Fix default value field serializer for marketplace offering options.

opennode/nodeconductor-assembly-waldur,opennode/nodeconductor-assembly-waldur,opennode/waldur-mastermind,opennode/nodeconductor-assembly-waldur,opennode/waldur-mastermind,opennode/waldur-mastermind,opennode/waldur-mastermind