Adds a wait timer between each VM migration during a flush action,
based on the state of the target VM. This causes each state change
command to wait until the last VM has completed its migration,
preventing all a node's VMs from being migrated to the same "least
RAM" hypervisor at once before any start to migrate.
Fixes#6
Fixes a bug whereby lasthypervisor would be empty because a VM had
never migrated before. This situation should never matter in an
actually-migrated VM since the ZK value would be set and as such
is simply discarded.
Joshua Boniface