Fix collections on transaction query.

[mikereiche]

Closes #1569.

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[daschl]

Should @programmatix also review this?

[mikereiche]

Yes, @programmatix could review it as well. For some reason I can't select him as a reviewer.

[mikereiche]

I'm going to merge this without review from @programmatix as he is feeling under the weather today.

[programmatix]

The TransactionAttemptContext.query overload that takes a Scope doesn't explicitly mark that as being @nullable (and in fact arguably should be checking it's not-null), so it would be less brittle if this code followed the specced API like so:

if (rs.name.equals(DEFAULT_SCOPE)) {
  ctx.query(statement, opts);
}
else {
  ctx.query(rs, statement, opts);
}

But it's ok. I'll just have to be careful to never change my interface to require scope to be non-null.