add support for k8s service type='LoadBalancer'

Setting K8S service type field to 'LoadBalancer' will provision a load balancer for a service, information about the provisioned balancer (external IP) will be published in the service's 'status.loadbalancer' field.

Traffic from the external load balancer will be directed at the backend Pods.

KURYR should support the following use cases :

1. load-balancer where ‘loadBalancerIP’ should be allocated from pre-defined pool.

for that case the K8s service spec should include the following :

"
kind: Service
apiVersion: v1
metadata:
  name: my-service
spec:
  type: LoadBalancer
"

2. Load-balancer with ‘loadBalancerIP’ specified by the user

for this option, the K8s service spec should include the following :

"
kind: Service
apiVersion: v1
metadata:
  name: my-service
spec:
  type: LoadBalancer
  loadBalancerIP: 1.2.3.4
"