Fix guarding of MySQL's numRows()

Authored by tstarling on Oct 8 2018, 3:46 AM.


Fix guarding of MySQL's numRows()

It can be true for successful write queries, not just false.

f3a197e49b785 introduced a caller which calls numRows() on the return
value of CREATE TEMPORARY TABLE queries, and it improved guarding of
numRows() in the PostgreSQL and SQLite cases accordingly, but it
neglected MySQL.

Bug: T201900
Change-Id: I8ae754a2518d9e47b093c31c20d98daaba913513