generator: order initrd fsck-root after local-fs-pre

generator: order initrd fsck-root after local-fs-pre

The initrd version of systemd-fsck-root.service must wait for
local-fs-pre.target just like systemd-fsck@.service to prevent
modifications to the filesystem prior to resuming from hibernation.
As-is my laptop routinely fails to resume due to fsck errors. The rest
of the time it is probably silently corrupting the filesystem.

Unlike normal boot, in the initrd systemd-fsck-root.service has no
special significance so it needs to be kept in sync with
systemd-fsck@.service. The name systemd-fsck-root.service is only used
to preserve state across switch-root.