Add support for virtblk type block devices as valid disks for pool creation

[salilhpe]

Describe the bug
I am trying to setup mayastor on a ubuntu VM running in KVM, the disk that I want to add is /dev/vdb, however kubectl get mayastor block-devices does not list this device. Tough I can create the diskpool with this device.
If I do a call with the --all flag I get:
/dev/vdb disk 2TiB no /devices/pci0000:00/0000:00:02.4/0000:05:00.0/virtio3/block/vdb 252 16 "/dev/disk/by-path/pci-0000:05:00.0", "/dev/disk/by-path/virtio-pci-0000:05:00.0"

To Reproduce
Setup mayastor on KVM VM

Expected behavior
block-devices should show the available disks.

Screenshots
block devices in /proc/devices
Block devices:
7 loop
8 sd
9 md
11 sr
65 sd
66 sd
67 sd
68 sd
69 sd
70 sd
71 sd
128 sd
129 sd
130 sd
131 sd
132 sd
133 sd
134 sd
135 sd
252 virtblk
253 device-mapper
254 mdp
259 blkext

And vdb is using 252.
$ ls -l /dev/block |grep vdb
lrwxrwxrwx 1 root root 6 Sep 12 10:32 252:16 -> ../vdb

** OS info (please complete the following information):**

• Distro: Ubuntu
• Kernel version
• MayaStor revision or container image :2.5.1

Additional context
Add any other context about the problem here.

[tiagolobocastro]

This is now available as of 2.7.1