cgroup: Also set blkio.bfq.weight

Commit [1] added a workaround when unified cgroups are used but missed
legacy cgroups where there is the same issue.

[1] <https://github.com/systemd/systemd/commit/2dbc45aea747f25cc1c3848fded2ec0062f96bcf

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Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
(cherry picked from commit 35e7a62c)
(cherry picked from commit 163e7eb9)