Return a VM failover plan assuming a given subset of hosts fail

Return value
	type	description
	Map[VM,Map[string,string]]	VM failover plan: a map of VM to host to restart the host on
Parameters
name	type	description
session_id	session	valid session reference
failed_hosts	Set[host]	The set of hosts to assume have failed
failed_vms	Set[VM]	The set of VMs to restart
Errors
name	arguments	description

• Message has only a synchronous version
• This is a custom message