Handle NotFoundException when listing floating IPs

Asking for floating IPs on an undercloud results in a NotFoundException.
Make openstackclient handle it gracefully.

No test is added for this because it would need to be a scenario test -
deploying a cloud without the foalting IP extension loaded.  I don't
think this edge case is worth an entire new job just to exercise it.

Change-Id: I73b544853376d98ab0dbb14e32fefc43c1a8a179
Story: 2006863

openstackclient/network/v2/floating_ip.py

@@ -12,6 +12,7 @@
 
 """IP Floating action implementations"""
 
+from openstack import exceptions as sdk_exceptions
 from osc_lib import utils
 from osc_lib.utils import tags as _tag
 
@@ -390,7 +391,10 @@ class ListFloatingIP(common.NetworkAndComputeLister):
 
         _tag.get_tag_filtering_args(parsed_args, query)
 
-        data = client.ips(**query)
+        try:
+            data = list(client.ips(**query))
+        except sdk_exceptions.NotFoundException:
+            data = []
 
         return (
             headers,