Volume support for multi hypervisors

In multi hypervisor OpenStack environment using such as KVM, VMware, Hyper-V etc, we need to provide Cinder storage
backends corresponding to these hypervisors for booting an instance from a volume. For example, VMware needs VMDK Cinder backend, Hyper-V needs Windows Cinder backend and also KVM needs supported backends such as LVM, ceph etc. KVM can't boot from VMDK backend.

However, there is no way to specify storage backend when user boot an instance from a volume. As a result, the boot volume
might be created on unrelated backend then the volume boot will fail.

To boot an instance from specific combination between hypervisor and storage backend properly, Cinder needs to know which hypervisor will handle the volume and then Cinder should schedule volume creation to proper storage backend based on the hypervisor type.