Make clear which statement is used.

Swapping always with all statement is not clear at all.

Signed-off-by: Frediano Ziglio <freddy77@gmail.com>
Improve mars1 test to use transaction

Test if transaction and MARS works together.

Problem and initial patch by Matt Lilley.

Signed-off-by: Frediano Ziglio <freddy77@gmail.com>
Remove too strict test.

Does not work using MARS. TDSSOCKET get reused so IRD is not always in
sync.

Signed-off-by: Frediano Ziglio <freddy77@gmail.com>
Use common transaction descriptor for all sessions in a connection.

If MARS is enabled and multiple sessions are used with transaction all
sessions have to have a valid transaction descriptor. So as MS driver
share the same descriptor across sessions.

Problem and initial patch by Matt Lilley.

Signed-off-by: Frediano Ziglio <freddy77@gmail.com>