Introduce ReclaimPolicy for ephemeral VirtualIP

[Rohit-0505]

• Add ReclaimPolicy for ephemerally created virtualIP resource with below supported modes:
  • Retain: the resource is not deleted after the managing resource has been deleted
  • Delete: the current behavior, the resource is garbage-collected when the managing resource has been deleted
• The default ReclaimPolicy is considered Delete not to break current behavior.
• Add wrapper type for VirtualIPTemplateSpec to support ReclaimPolicy type along with existing VirtualIPSpec
• OwnerReference is set to an ephemerally created virtualIP with ReclaimPolicyTypeDelete.
• To prevent deletion of ephemeral vip without ownerReference a RESTDeleteStrategy method ValidateDelete is added in the strategy.go
• Add Test cases
  [Note: virtualIP_release_controller is already taking care of releasing virtualIP whose claimer doesn't exist, by setting .spec.targetRef to nil when claimer NetworkInterface object is deleted. So not adding any extra logic for this]

Fixes #1115