These are the remaining resources that support "tag on create" of which we werent taking advantage.
This allows more fine-grained IAM permissions for the kops cli.
SubnetMappings allow to explicitely set the private IPv4 address that
must be used for the NLB.
SubnetMappings and Subnets in the AWS API are compatible as long as the
address settings are not changes, making this commit backwards compatible.