Revert "Refactor configuring of floating ips on a router."

This patch breaks gating job.
Because nat rule for metadata will be only added on the
router_add.
Revert it for now.

Fixes bug 1211829
This reverts commit 9382ee659212285a203550cf60476dd146d27a29.

Change-Id: I05925798cddc7a706e922025ef6ce27b6638ffb6
Merge "Revert "Refactor configuring of floating ips on a router.""