qubes.ResizeDisk: handle dmroot being a symlink

In non-template-based-VMs it can be just a symlink (depending on
initramfs version).

qubes-rpc/qubes.ResizeDisk

@@ -13,6 +13,7 @@ case $disk_name in
     root)
         # force some read to refresh device size
         head /dev/xvda > /dev/null
+        if [ "$(stat -Lc %t /dev/mapper/dmroot)" != "ca" ]; then
             new_size=$(cat /sys/block/xvda/size)
             ro=$(/sys/block/xvda/ro)
             if [ "$ro" -eq 1 ]; then
@@ -22,6 +23,7 @@ case $disk_name in
             fi
             dmsetup load dmroot --table "$new_table"
             dmsetup resume dmroot
+        fi
         resize2fs /dev/mapper/dmroot
         ;;
     *)