chromeos-init-systemd: Initialize device mapper devs

Device mapper udev rules assume that devices are pre-initialized with
DM_UDEV_PRIMARY_SOURCE_FLAG. This is only true for devices that are
created with libdevmapper. COS dm-verity devices are not created with
libdevmapper; they are created by the kernel using the "dm-mod.create"
kernel command line behavior.

The device mapper udev rules respond to "change" uevents regardless of
the DM_UDEV_PRIMARY_SOURCE_FLAG. To properly initialize device mapper
devices in udev, we can trigger a change message for available device
mapper devices on boot.

BUG=b/186546612
TEST=presubmit
RELEASE_NOTE=None

Change-Id: I51f8c67d7363b493e03a3664b18fb3a5cc25a450
Reviewed-on: https://cos-review.googlesource.com/c/cos/overlays/board-overlays/+/16036
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Reviewed-by: Anil Altinay <aaltinay@google.com>
4 files changed