Fix rounding error in htex block scale in #3721
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Description
PR #2196 calculates a number of blocks to scale in, in the htex strategy, rather than scaling in one block per strategy iteration. However, it rounds the wrong way: it scales in a rounded up, rather than rounded down, number of blocks.
Issue #3696 shows that then resulting in oscillating behaviour: With 14 tasks and 48 workers per block, on alternating strategy runs, the code will either scale up to the rounded up number of needed blocks (14/48 => 1), or scale down to the rounded down number of needed blocks (14/48 => 0).
This PR changes the rounding introduced in #2196 to be consistent: rounding up the number of blocks to scale up, and rounding down the number of blocks to scale down.
Changed Behaviour
HTEX scale down should oscillate less
Fixes
Fixes #3696
Type of change