support data integrity checking

[ddiss]

it'd be helpful to have esxi_ceph_chaos_monkey (eccm) checking data integrity at various stages and layers during a test run:

• application
  • use fio's built in verification functionality, running on the test VM
• guest filesystem
  • use "btrfs scrub" for metadata and data integrity checking
• VMFS
  • use VOMA to check metadata consistency
  • https://kb.vmware.com/s/article/2036767

Each of these would require quite some work. fio verification should be fine as a starting point.