netaddr: fix IP conversion issues with netaddr>1.0.0

netaddr 1.0.0 and above changed the way things are
converted to IPs (see [1]), make Horizon work
after bumping to this new version (see [2])

[1]: https://netaddr.readthedocs.io/en/latest/changes.html#release-1-0-0
[2]: https://review.opendev.org/c/openstack/requirements/+/909300

Change-Id: I3d7da8ef919f0607a1d32e2b28760e95449b4eaa

horizon/forms/fields.py

@@ -89,7 +89,11 @@ class IPField(fields.Field):
 
         try:
             if self.mask:
-                self.ip = netaddr.IPNetwork(value)
+                try:
+                    self.ip = netaddr.IPNetwork(value.strip())
+                except netaddr.AddrFormatError:
+                    self.ip = netaddr.IPNetwork(
+                        netaddr.cidr_abbrev_to_verbose(value.strip()))
             else:
                 self.ip = netaddr.IPAddress(value)
         except Exception: