kvm: Assume proper type for booleans

It's ok to fail fast if bad parameters are provided by the user, and since
json-in-xml is used, more restrictions are welcomed.
3 jobs for feature/kvm-move-to-json-in-xml in 0 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  External
canceled SlapOS.SoftwareReleases.IntegrationTest-py3-luke/feature/kvm-move-to-json-in-xml

35:14:11

running SlapOS.SoftwareReleases.IntegrationTest-py3-luke/feature/kvm-move-to-json-in-xml

17209:23:52

failed SlapOS.SoftwareReleases.IntegrationTest-py3-luke/feature/kvm-move-to-json-in-xml

100:54:44