Use separate memoized KafkaConsumer for choose_best_partition_for_topic
Use separate memoized KafkaConsumer for choose_best_partition_for_topic

Reinstantiating the KafkaConsumer on each form and case change seems to
be resulting in a low rate of failures of the "smart" partitioning. Not
a P1 or anything because it falls back to default partitioning.

dimagi/commcare-hq,dimagi/commcare-hq,dimagi/commcare-hq,dimagi/commcare-hq,dimagi/commcare-hq