add the ability to add hybrid ipv4/6 networks

[ramonskie]

currently google cpi only accepts 1 network interface see https://github.com/cloudfoundry/bosh-google-cpi-release/blob/master/src/bosh-google-cpi/google/instance_service/networks.go#L30

added with commit https://github.com/cloudfoundry/bosh-google-cpi-release/commit/de69e9c3db7a66f90e6f56a94f2e3c435d69338b

a dualstack is availble in gcp docs see https://cloud.google.com/compute/docs/ip-addresses/configure-ipv6-address#create-vm-ipv6

[ramonskie]

it seems that aws only support 1 network https://github.com/cloudfoundry/bosh-aws-cpi-release/blob/master/src/bosh_aws_cpi/lib/cloud/aws/instance_param_mapper.rb#L95