This PR fixes issues in TableDatabase.
TableDatabase is a wrapper of underlying ethdb.Database with an additional prefix.
The prefix is applied to all entries it maintains. However when we try to retrieve entries
from it we don't handle the key properly. In theory the prefix should be truncated and
only user key is returned. But we don't do it in some cases, e.g. the iterator and batch
replayer created from it. So this PR is the fix to these issues.
gary rong