Fix dynamic IPv6 rules showing junk for non-specified address masks.

Fix dynamic IPv6 rules showing junk for non-specified address masks.

For example:
  00002      0         0 (19s) PARENT 1 tcp 10.10.0.5 0 <-> 0.0.0.0 0
  00002      4       412 (1s) LIMIT tcp 10.10.0.5 25848 <-> 10.10.0.7 22
  00002     10       777 (1s) LIMIT tcp 2001:894:5a24:653::503:1 52023 <-> 2001:894:5a24:653:ca0a:a9ff:fe04:3978 22
  00002      0         0 (17s) PARENT 1 tcp 2001:894:5a24:653::503:1 0 <-> 80f3:70d:23fe:ffff:1005:: 0

Fix this by zeroing the unused address, as is done for IPv4:
  00002     0         0 (18s) PARENT 1 tcp 10.10.0.5 0 <-> 0.0.0.0 0
  00002    36     14952 (1s) LIMIT tcp 10.10.0.5 25848 <-> 10.10.0.7 22
  00002     0         0 (0s) PARENT 1 tcp 2001:894:5a24:653::503:1 0 <-> :: 0
  00002     4       345 (274s) LIMIT tcp 2001:894:5a24:653::503:1 34131 <-> 2001:470:1f11:262:ca0a:a9ff:fe04:3978 22

MFC after:	2 weeks