Currently, var-lib-scylla.mount may fails because it can start before
MDRAID volume initialized.
We may able to add "After=dev-disk-by\x2duuid-<uuid>.device" to wait for
device become available, but systemd manual says it automatically
configure dependency for mount unit when we specify filesystem path by
"absolute path of a device node".
So we need to replace What=UUID=<uuid> to What=/dev/disk/by-uuid/<uuid>.
Fixes#8279Closes#8681
(cherry picked from commit 3d307919c3)
b81919dbe2