Allow Selection Of Pre-existing Floating IP

[XaverStiensmeier]

Currently, BiBiGrid will use existing floating IPs or create one of its own. The floating IP used is then deleted afterwards. This is problematic whenever a DNS points toward the IP.

To fix this the cloud specific floatingIpId key will be introduced that allows explicitly setting the floating ip. Otherwise, a new one is generated.

• Rewrite Floating IP attachment to allow passing of a specific floating ip by id
• Only delete floating IP of a cluster if floating_ip not set in the configuration
• Check for floating IP existence during check
• Add floating_ip parameter to REST terminate call
• Update Tests