Fix ordering of urls in workqueues when priorities < 0 are used.
Because the ordering is done strictly binary, negative values will come
last, because their binary representation starts with the MSB at 1. In
order to fix this, we'll have to add the minimum byte value to become 0.
This means that the maximum number will become out of range in
Byte-value, but the integer value is nicely converted down to the actual
binary representation that is useful here.