Support for Elastigroups [SpotInst] ignores VPCZoneIdentifier

[mo-gr]

When the Appserver has a VPCZoneIdentifier configuration, like:

VPCZoneIdentifier:
          Fn::FindInMap:
            - LoadBalancerSubnets
            - Ref: AWS::Region
            - Subnets

This should be translated to the Elastigroup create argument compute.subnetIds.

Currently, this does not happen, resulting in instances being potentially created in the wrong subnets.

A workaround is to explicitly specify the compute.subnetIds argument in the Elastigroup configuration:

Elastigroup:
  compute:
    subnetIds:
      Fn::FindInMap:
            - LoadBalancerSubnets
            - Ref: AWS::Region
            - Subnets