Used instance uuid rather than id in remove-fixed-ip
Used instance uuid rather than id in remove-fixed-ip

remove-fixed-ip called db method fixed_ip_get_by_instance. but
fixed_ip_get_by_instance use instance uuid not id, so change to
uuid in remove-fixed-ip.

Fixed bug: #1065899

Change-Id: Ic7526c7e91933424c04be9bb91d4a98cfedd9b01
(cherry picked from commit 66521a1571f0922f791ae7f405129fb99b870f38)

paulmathews/nova,paulmathews/nova,paulmathews/nova