Remove 'floating_ips' extension attribute to POST /servers API call.
Instead use the 'fixed_ip' attribute of 'networks' attribute to specify
the IPv4 address of a floating IP. So in order to create a server
connected to a private network and a public network, the 'networks'
attribute will be:
[{"uuid": "<private-network-uuid>"},
 {"uuid": "<floating-ip-network-uuid>",
  "fixed_ip": "<floating-ip-address>"}]