Releasing Public IPs via cloud.terminate_instances

cloud.terminate_instances() now releases the public_ip associated
with the instance, if any.

Signed-off-by: Shashank Sahni <shredder12@gmail.com>
removed public_ip release from cluster.delete

Signed-off-by: Shashank Sahni <shredder12@gmail.com>
Releasing Public IPs via cloud.terminate_instances

cloud.terminate_instances() now releases the public_ip associated
with the instance, if any
.
Signed-off-by: Shashank Sahni <shredder12@gmail.com>