Disk auto-selection sometimes do not work

[bohanyang]

Link to #101

(on VirtFusion) It seems that /dev/sda is selected rather than the main disk /dev/vda.

Disk /dev/vda: 40 GiB, 42949672960 bytes, 83886080 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 4B476DA3-A9DF-4327-A2D2-7E14E01CB37E

Device      Start      End  Sectors  Size Type
/dev/vda1    2048     4095     2048    1M BIOS boot
/dev/vda2    4096   253951   249856  122M EFI System
/dev/vda3  253952 83886046 83632095 39.9G Linux filesystem


Disk /dev/sda: 368 KiB, 376832 bytes, 736 sectors
Disk model: QEMU HARDDISK
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes