Service loadbalancerIP could be one of the following :
1. loadbalancerIP allocated from pre-defined pool
k8s service.spec.type = 'LoadBalancer'
2. loadbalancerIP specified by user
k8s service.spec.type = 'LoadBalancer' and service.spec.loadBalancerIP='x.y.z.t'
This commit extend service capability to support '1' and '2'
Implements: blueprint k8s-service-type-loadbalancer
Change-Id: I98f56692e143aa7ab14dd9920139819c7026acce