live-boot failed mount persistence media when use uuid

[TQ]

live-boot failed if set live-media with value `/dev/disk/by-uuid/xxxx-xxxx-xxx. it can success mount the rootfs with squash file, but when try to mount persistence partition in the same media it will failed to find the mount point which already mount for the squash at `/run/live/medium`. then the mount persistence will failed by busy, so the fix is much easy.

file: /lib/live/boot/9990-misc-helpers.sh
where_is_mounted ()
{
 device=${1}
 # return first found
- grep -m1 "^${device} " /proc/mounts | cut -f2 -d ' '
+ uuid=/dev/disk/by-uuid/$(blkid -o value -s UUID ${device})
+ grep -m1 "^${device} \|^${uuid} " /proc/mounts | cut -f2 -d ' '
}

please check.
Thanks