Accepts UUID as an ID of Floating IP

Fixes bug 1052561.

In Quanutm, Floating IPs are identified by UUID instead of integer ID.
After quantum-nova integration for FLoating IP has been implemented,
Horizon also needs to accept UUID style of ID for Floating IP.

Change-Id: I6ed919cbbc818c97cecef2fe3a91c8e5a7ac76e0
(cherry picked from commit 7ab5ace768797f56bf7e1c846fca0f1d40ed6086)
Merge "Accepts UUID as an ID of Floating IP" into stable/folsom