Commit offsets in Consumer#each_batch even if we don't read any new messages.
Commit offsets in Consumer#each_batch even if we don't read any new messages.

This is similar to a83fddfcf84e01d2f242452caa8b8a7507493916 which was applied to Consumer#each_message and ensures that offsets are retained even if we don't receive any new messages for longer than the offset retention period.

zendesk/ruby-kafka,zendesk/ruby-kafka