send "423 Interval too small" Response to Subscribe with Expires less that min allowed

[RFC3265]3.1.6.1....
   The notifier MAY also check that the duration in the "Expires" header
   is not too small.  If and only if the expiration interval is greater
   than zero AND smaller than one hour AND less than a notifier-
   configured minimum, the notifier MAY return a "423 Interval too
   small" error which contains a "Min-Expires" header field.  The "Min-
   Expires" header field is described in SIP [1].




git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@278536 65c4cc65-6c06-0410-ace0-fbb531ad65f3