ipv6: add link-local, sit and loopback address with INFINITY_LIFE_TIME

In the past the IFA_PERMANENT flag indicated, that the valid and preferred
lifetime where ignored. Since change fad8da3e

 ("ipv6 addrconf: fix
preferred lifetime state-changing behavior while valid_lft is infinity")
we honour at least the preferred lifetime on those addresses. As such
the valid lifetime gets recalculated and updated to 0.

If loopback address is added manually this problem does not occur.
Also if NetworkManager manages IPv6, those addresses will get added via
inet6_rtm_newaddr and thus will have a correct lifetime, too.

Reported-by: François-Xavier Le Bail <fx.lebail@yahoo.com>
Reported-by: Damien Wyart <damien.wyart@gmail.com>
Fixes: fad8da3e

 ("ipv6 addrconf: fix preferred lifetime state-changing behavior while valid_lft is infinity")
Cc: Yasushi Asano <yasushi.asano@jp.fujitsu.com>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>