fix(DBAPI): keep cursor hot when statement is a script

[mistercrunch]

all the details here: #377

I guess technically a script isn't DML

[tswast]

Makes sense to me.

Actually, we can probably consider removing the is_dml logic altogether now that we moved to getQueryResults instead of tabledata.list (#375). The destination table of a DML query would return a non-null value that was unreadable or would return nonsense with DML (and some DDL) queries. Before we do that, I'll want to double-check that we have a system test for this case. (I think a DDL to CREATE VIEW would be a good choice for that)

[mistercrunch]

Superseded by #387