Bug 32408: Add unit tests to SIP checkout

Bug 32408: Add unit tests to SIP checkout

This patch adds unit tests to show SIP's behavior on checkout according to the
AllFinesNeedOverride, AllowFineOverride and noissuescharge sysprefs, knowingly:

+----------------------+-------------------+---------+---------+
| AllFinesNeedOverride | AllowFineOverride |  Under  |  Over   |
+----------------------+-------------------+---------+---------+
|                    0 |                 0 | allowed | blocked |
|                    0 |                 1 | allowed | blocked |
|                    1 |                 0 | blocked | blocked |
|                    1 |                 1 | blocked | blocked |
+----------------------+-------------------+---------+---------+

(the columns Under and Over are referring to "under noissuescharge" and
"over noissuescharge")

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>