…ionSettings` as repeated value

Rosco manages `virtualizationSettings` for `aws` as a list of settings where
an item contains regional VM settings, like follows.

    aws:
      bakeryDefaults:
        baseImages:
        - baseImage:
            id: ubuntu
            shortDescription: v12.04
            detailedDescription: Ubuntu Precise Pangolin v12.04
            packageType: deb
            templateFile: aws-ebs.json
          virtualizationSettings:
          - region: us-east-1
            virtualizationType: hvm
            instanceType: t2.micro
            sourceAmi: ami-d4aed0bc
            sshUserName: ubuntu
            spotPrice: "0"
            spotPriceAutoProduct: Linux/UNIX (Amazon VPC)

I have confirmed that testdata also contains wrong schema around
`virtualizationSettings`. As long as I could confirm from Rosco
implementation, it had `virtualizationSettings` was typed as
 `List<AWSVirtuzliationSettings>`, therefore, I do believe
this is mistake while generating testdata for `aws` provider.

    static class AWSBakeryDefaults {
      String awsAccessKey
      String awsSecretKey
      String awsSubnetId
      String awsVpcId
      Boolean awsAssociatePublicIpAddress
      String templateFile
      BakeRequest.VmType defaultVirtualizationType
      List<AWSOperatingSystemVirtualizationSettings> baseImages = []
    }

    static class AWSOperatingSystemVirtualizationSettings {
      BakeOptions.BaseImage baseImage
      List<AWSVirtualizationSettings> virtualizationSettings = []
    }

https://github.com/spinnaker/rosco/blob/version-0.25.0/rosco-core/src/main/groovy/com/netflix/spinnaker/rosco/providers/aws/config/RoscoAWSConfiguration.groovy#L65

…es[].virtualizationSettings` as plural