Fix some bug in reducer

[oraluben]

cc @suyZhong

[suyZhong]

I suppose we'd better use false here. Otherwise, the reduce log would keep increasing.

[suyZhong]

The actual issue is at L495-497. I think the logger there is not for the newGlobalState

[suyZhong]

Just a few suggestions,

1. We could replace the currentFileWriter when reducing since we don't need to write to -cur.log anymore
2. Currently the exception log （database.log） only shows DDL&DML statements after reducing. I hope except for the general "check reduce.log", I could also see the reduced query in it. We could somehow keep the error messages (Assertion when finding a bug) in the reproducer and add this message at here:

   sqlancer/src/sqlancer/Main.java

   Line 501 in 201fd4c

   throw new AssertionError("Found a potential bug, please check reducer log for detail.");