Fix typos and unused statements
fix for issue 320: no output when max_cdate is used for dataset API. Fix for issue: 325 noe instead of 0 return when no match found for listBlockSummaries API.
Remove duplicated blocks from migration dict
Merge pull request #335 from yuyiguo/issue-320

fix for issue 320: no output when max_cdate is used for dataset API. Fix...
Merge pull request #336 from giffels/dbs3-migration-hot-fix

Dbs3 migration hot fix