lsblk: Fall back to ID_SERIAL

lsblk: Fall back to ID_SERIAL

In some cases ID_SERIAL_SHORT isn't provided by libudev, but ID_SERIAL
is. An example of this are virtio devices. See the output of udevadm
info:
P: /devices/pci0000:00/0000:00:06.0/virtio2/block/vdb
N: vdb
S: disk/by-id/virtio-08491434ee711d3420e9
S: disk/by-path/pci-0000:00:06.0
S: disk/by-path/virtio-pci-0000:00:06.0
E: DEVLINKS=/dev/disk/by-id/virtio-08491434ee711d3420e9 /dev/disk/by-path/pci-0000:00:06.0 /dev/disk/by-path/virtio-pci-0000:00:06.0
E: DEVNAME=/dev/vdb
E: DEVPATH=/devices/pci0000:00/0000:00:06.0/virtio2/block/vdb
E: DEVTYPE=disk
E: ID_PATH=pci-0000:00:06.0
E: ID_PATH_TAG=pci-0000_00_06_0
E: ID_SERIAL=08491434ee711d3420e9
E: MAJOR=252
E: MINOR=16
E: SUBSYSTEM=block
E: TAGS=:systemd:
E: USEC_INITIALIZED=1403804

[kzak@redhat.com: - add ID_SERIAL also to get_properties_by_file()]

Signed-off-by: Karel Zak <kzak@redhat.com>