regression framework test: test result of each iterations

@xiaoyunwu @xiang90 

This is my fix upon Xiaoyun's previous work on testing regression framework.
The problem that Xiaoyun encountered before was caused:
1. Xiaoyun was getting only 10 data results from the channel
2. The channel actually spins off 11 data results. So it's not finished. It will call IncEpoch one last time.
3. But the test has finished, shutting down etcd server, causing IncEpoch "Key not found" error.