Currently an admin can choose which host a VM is to be started on.
They should be able to 'override' the allocation algorthm to a greater
or lesser extent at will, and be able to choose the pod, cluster or host
that they wish a new VM to be deployed in.
DeployVirtualMachine API has been extended with additional, optional
parameters podid and clusterid that will be passed to and used in the
deployment planner, when selecting a viable host. If the user supplies
a pod, a suitable host in the given pod will be selected. If the user
supplies a cluster, a suitable host in the given cluster will be selected.
Based on the parameter supplied and on passing validation, the VM will
then be deployed on the selected host, cluster or pod.
