This will allow to be sure globally, that production code is generating
correct documents.

As getFullcomputerInformation is used by slap library, there will be always
something transmitted.

getSoftwareReleaseList is updated by getFullComputerInformation call, which
returns everything, even destroyed (and theoretically forgotten) software
releases.

This will allow portal_deliveries/vifib_sale_invoice_builder to put movements
on prepared invoice.

Currently packing lists are created faster, and this test method is used in
tests which are requesting stopped and started instances.

Drop not needed SlaveInstanceStopComputerPartitionInstallation.

Directly provide the instance document in the request.

Created instance can be now accessed directly from request.

Also rename expected exception.

It is hard to remove elements from sequence, and get will return value of
available key, but resetting sets to '', so fallback again to started state.

Previous steps can set state to unexpected value.