Fixes AttributeError of FloatingIPPollster

Currently FloatingIPPollster is using Nova client to get floating
IP metrics instead of accessing OpenStack DB directly. So there are
some attributes can't be accessed from Nova /os-floating-ips REST API.
In this fix, those attributes usage will be removed temporarily.
And they will be back after fix the Nova bug 1174802.

Fixes bug 1173845

Change-Id: I61572c50db6f90c26bbdb7da5f0e9a249b405e58
Merge "Fixes AttributeError of FloatingIPPollster"