Fix bugzilla # 1208

Fix bugzilla # 1208

Winbind tickets expired.  We now check the expiration time, and acquire
new tickets.  We couln't rely on renewing them, because if we didn't get
a request before they expired, we wouldn't have renewed them.  Also, there
is a one-week limit in MS on renewal life, so new tickets would have been
needed after a week anyway.   Default is 10 hours, so we should only be
acquiring them that often, unless the configuration on the DC is changed (and
the minimum is 1 hour).
(This used to be commit c2436c433afaab4006554a86307f76b6689d6929)