Bug 15553: [QA Follow-up] Replace hardcoded tmp and add instance to dirname

Bug 15553: [QA Follow-up] Replace hardcoded tmp and add instance to dirname

If you use multiple instances on one server, you could have the situation
that instance A creates the cgisess subfolder and instance B could have a
permission problem. This patch resolves that by allowing each instance to
have its own cgisess subfolder.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Brendan A Gallagher <brendan@bywatersolutions.com>
(cherry picked from commit c4934b2dab427da4304913b3f0f26e0a24606896)
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>