Misc. small changes to address PR feedback
Misc. small changes to address PR feedback

- Make test function names more verbose (for targeting with -run)
- safeClose io.Closers to catch errors
- Remove debugging time.Sleep call
- Don't use globals for client, brokers, etc.

winlinvip/sarama,kmiku7/sarama,raisemarketplace/sarama,mailgun/sarama,jimmykuo/sarama,DataDog/sarama,jepst/sarama,cep21/sarama,winlinvip/sarama,Shopify/sarama,HelixEducation/sarama,yangfan876/sarama,scalingdata/sarama,yangfan876/sarama,crast/sarama,VividCortex/sarama,cep21/sarama,jepst/sarama,VividCortex/sarama,pronix/sarama,remerge/sarama,vrischmann/sarama,Neuw84/sarama,kmiku7/sarama,pronix/sarama,Shopify/sarama,jimmykuo/sarama,Neuw84/sarama,crast/sarama,scalingdata/sarama,DataDog/sarama,HelixEducation/sarama,remerge/sarama,vrischmann/sarama,raisemarketplace/sarama,mailgun/sarama