remove qcow2 and virtualbox disk image

nobody should use them, because it's insecure.
7 jobs for master in 22 seconds (queued for 261 minutes and 51 seconds)
latest
Status Job ID Name Coverage
  Lint
passed #2178
flake8

00:00:20

passed #2175
shellcheck

00:00:17

passed #2176
shfmt

00:00:13

passed #2179
validate-packer

00:00:18

passed #2177
yapf

00:00:14

 
  Build
failed #2180
secure-kvm
build:qemu

failed #2181
secure-virtualbox
build:virtualbox

 
Name Stage Failure
failed
build:virtualbox Build There has been a timeout failure or the job got stuck. Check your timeout limits or try again
No job log
failed
build:qemu Build There has been a timeout failure or the job got stuck. Check your timeout limits or try again
No job log