Ensure channel state is not incorrectly set in the case of a very early answer.

The needringing bit was being read in dahdi_read after answering thereby
setting the state to ringing from up. This clears needringing upon answering
so that is no longer possible.

(closes issue #17067)
Reported by: tzafrir
Patches: 
      needringing.diff uploaded by tzafrir (license 46)


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@260434 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_dahdi.c

@@ -4445,7 +4445,7 @@ static struct ast_frame *dahdi_handle_event(struct ast_channel *ast)
 					p->subs[index].f.frametype = AST_FRAME_CONTROL;
 					p->subs[index].f.subclass = AST_CONTROL_ANSWER;
 					/* Make sure it stops ringing */
-					dahdi_set_hook(p->subs[index].dfd, DAHDI_OFFHOOK);
+					p->subs[SUB_REAL].needringing = 0;
 					ast_log(LOG_DEBUG, "channel %d answered\n", p->channel);
 					if (p->cidspill) {
 						/* Cancel any running CallerID spill */