Bug 10574 - mute the "upgrading from 3.2" message

New installs get the message about running a script if upgrading from
3.2. They shouldn't. This silences this message in all cases except when
you actually are upgrading from 3.2.

Test plan:

There are three scenarios to test:
1) A fresh install should not cause the prompt.
2) An upgrade with or without the debconf entry set should not cause the
   prompt.
3) An upgrade from a 3.2 release to this should cause the prompt.

To remove the debconf entry that says the prompt has been seen:

echo 'unregister koha-common/3.2-3.4-upgrade-notice' | sudo debconf-communicate koha-common

This should be run before every test to make debconf forget that it's
shown the prompt. To get its current state:

sudo debconf-show koha-common

To test against the 3.2 version, an empty package that claims to be Koha
3.2.2 is attached to the bug.

Signed-off-by: Mirko Tietgen <mirko@abunchofthings.net>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>