windows: Add missing return

We were logging in a code path but not setting a return value. This was
passing tests because it seems 'assertFalse' does a falsey check, not a
true boolean False check.

Change-Id: If0156cd4d4c1acbad683873d632ee5afb0b7b7ad
Signed-off-by: Stephen Finucane <sfinucan@redhat.com>

os_vif/internal/ip/windows/impl_netifaces.py

@@ -30,6 +30,7 @@ class Netifaces(ip_command.IpCommand):
             return bool(netifaces.ifaddresses(device))
         except ValueError:
             LOG.warning("The device does not exist on the system: %s", device)
+            return False
         except OSError:
             LOG.error("Failed to get interface addresses: %s", device)
             return False