result rows for prepared statements if query cache is enabled.
If a placeholder ('?') is used in a prepared statement with SELECT query,
as the column field, it is used as the result column name.
Eg: SELECT ? FROM t1 where a=1;
If the same SELECT query is executed later without the placeholder and
turns out to be same as the previous query with the placeholder substituted,
it is identified as a cached query. Hence, the previous result column name
(with ?) is displayed in the result.

This test is intended to verify the working of prepared statements.
So it seems reasonable to disable this test when the QC is enabled, to avoid
the test failure notification.