[BUG] Fix using deprecated option of blockdev command in go-spdk-helper

[derekbit]

Describe the bug

Fix using deprecated option --getsize of blockdev command in go-spdk-helper.
Should use --getsz instead.

# blockdev -h

Usage:
 blockdev [-v|-q] commands devices
 blockdev --report [devices]
 blockdev -h|-V

Call block device ioctls from the command line.

Options:
 -q             quiet mode
 -v             verbose mode
     --report   print report for specified (or all) devices

 -h, --help     display this help
 -V, --version  display version

Available commands:
 --getsz                   get size in 512-byte sectors
 --setro                   set read-only
 --setrw                   set read-write
 --getro                   get read-only
 --getdiscardzeroes        get discard zeroes support status
 --getss                   get logical block (sector) size
 --getpbsz                 get physical block (sector) size
 --getiomin                get minimum I/O size
 --getioopt                get optimal I/O size
 --getalignoff             get alignment offset in bytes
 --getmaxsect              get max sectors per request
 --getbsz                  get blocksize
 --setbsz <bytes>          set blocksize on file descriptor opening the block device
 --getsize                 get 32-bit sector count (deprecated, use --getsz)
 --getsize64               get size in bytes
 --setra <sectors>         set readahead
 --getra                   get readahead
 --setfra <sectors>        set filesystem readahead
 --getfra                  get filesystem readahead
 --flushbufs               flush buffers
 --rereadpt                reread partition table

To Reproduce

Expected behavior

Support bundle for troubleshooting

Environment

• Longhorn version:
• Impacted volume (PV):
• Installation method (e.g. Rancher Catalog App/Helm/Kubectl):
• Kubernetes distro (e.g. RKE/K3s/EKS/OpenShift) and version:
  • Number of control plane nodes in the cluster:
  • Number of worker nodes in the cluster:
• Node config
  • OS type and version:
  • Kernel version:
  • CPU per node:
  • Memory per node:
  • Disk type (e.g. SSD/NVMe/HDD):
  • Network bandwidth between the nodes (Gbps):
• Underlying Infrastructure (e.g. on AWS/GCE, EKS/GKE, VMWare/KVM, Baremetal):
• Number of Longhorn volumes in the cluster:

Additional context

<!-Please add any other context about the problem here.-->

[longhorn-io-github-bot]

Pre Ready-For-Testing Checklist

• Where is the reproduce steps/test steps documented?
  The reproduce steps/test steps are at:

Attaching and detaching v2 volume should still work.

• Is there a workaround for the issue? If so, where is it documented?
  The workaround is at:

• Does the PR include the explanation for the fix or the feature?

• Have the backend code been merged (Manager, Engine, Instance Manager, BackupStore etc) (including backport-needed/*)?
  The PR is at

longhorn/go-spdk-helper#67

• Which areas/issues this PR might have potential impacts on?
  Area: v2 volume
  Issues

[innobead]

backend work.