Fixes issue in test_problem_layout_ticket_1128

Deleting the storedir breaks the test server by setting the remaining
free space to 0, and therefore the server will refuse any shares even
if the placement algorithm is correct. This removes the shares from
server 0 without corrupting its other properties.
Test now irrelevant

This situation shouldn't fail anymore
Adds edge case when happiness can't be met
Calculates maximum matching from readonly servers first

In order for happiness_upload to return a happiness of 3 on
test_problem_layout_ticket_1128 in test_upload.py, the readonly
servers must have a higher priority than other existing shares.