middleware.sizelimit: stop importing wsgi

This patches stops the sizelimit module to rely on the deprecated WSGI
module.

Change-Id: Ie804a74f833112f7d6d30f787f426d6f7ad0be2f
Remove extension_stubs

This file isn't used anywhere, let's get rid of it.

Change-Id: I13a1c81616697af2baa659ea6033061b2951602c
Enables db2 server disconnects to be handled pessimistically

A checkout listener can be added to sqlalchemy to be able to
handle database disconnect pessimistically and avoid an error in
the event of a DB restart or simply a temp connection issue due
to network glitches. At the moment only mysql is enabled with
this feature. This patch enables db2 as well.

Partial-Bug: #1231657
Change-Id: I5563360b43c4b648f5b035099b0e1d2e71d32503
Merge "Enables db2 server disconnects to be handled pessimistically"
Merge "middleware.sizelimit: stop importing wsgi"
Merge "Remove extension_stubs"