Fix the hardcoded us-east-1 region in clusters.go

[tnachen]

Currently in clusters.go we hard coded us-east-1:

`
// TODO: We assume region is us-east-1 and we assume Kubernetes only.
clusterDefinition := &deployer.ClusterDefinition{
Nodes: jobDeploymentConfig.GetNodes(),
}

    deployment := &deployer.Deployment{
            Region:            "us-east-1",
            Name:              "workload-profiler-" + applicationConfig.Name,
            NodeMapping:       []deployer.NodeMapping{},
            ClusterDefinition: *clusterDefinition,
            KubernetesDeployment: &deployer.KubernetesDeployment{
                    Kubernetes: []deployer.KubernetesTask{},
            },
    }

`
We are able to look up the region using the ec2metadata service (Refer to aws_sizing.go for example). We should call it once to get the region and az, and pass it to clusters.go and also aws sizing if needed.