what's the better name for kvm on Z and kvm on x86_64

[jinlings]

our application support zvm(s390x),kvm(x86_64), and kvm on Z,but we are not sure which name need to use for kvm on Z ,these short name are used in conf.json while installing cloudland, and in the meanwhile it's used in virt_type as well

Initial decision:
zvm(s390x) zvm
kvm(x86_64) kvm_x86 or kvm_amd64
kvm on Z kvm_s390x