Fixing issue with dimensions in aggregator

Change-Id: Ib8aa9c2822dae8eb8511a53798b0aa989599e34b
Improved error handling in kafka_consumer

If the kafka_consumer plugin encounters an error fetching consumer offsets
(like for a partition which is configured but no longer exists), it can
start to allocate threads and never close them oout.  I added additional
exception handling around fetching both consumer and broker offsets so
that the plugin will log errors, but not fail altogether, and not cause
runaway thread usage.

Change-Id: I03e6f7cc3ecd787d7b4ad54b74136540607a465a
Merge "Fixing issue with dimensions in aggregator"
Merge commit '41fab4e79a526389bbe6eda431b3bed866e1646f'