refactor network ip config in setup.sh
refactor network ip config in setup.sh

* we were obtaining the same ip in two different ways
** get first network and current ip
** get network with default section (which was coincedentally
   first) and get ip from it.

  BOSH expands network section and adds current instance ip as ip method.

Signed-off-by: Oleksandr Slynko <4e0b08036a6e8359453f77324c7b401fdae249da@pivotal.io>

pivotal-cf/cf-rabbitmq-release,pivotal-cf/cf-rabbitmq-release,pivotal-cf/cf-rabbitmq-release,pivotal-cf/cf-rabbitmq-release