This environment can be used with AllNodesExtraConfig to enable swap on
a device with the given label as specified by the swap_partition_label
parameter.
If Ironic is used to create the swap partition, the partition will have
a label of swap1, so that's a reasonable default for the parameter.
The partition is also written to /etc/fstab as a swap mount so that it
will be enabled on reboot.
Change-Id: I5cd68c13dbfe53eecf6c6ad93151eadc980a902d