[MEDIUM] session: better fix for connection to servers with closed input

The following patch fixed an issue but brought another one :
  296897 [MEDIUM] connect to servers even when the input has already been closed

The new issue is that when a connection is inspected and aborted using
TCP inspect rules, now it is sent to the server before being closed. So
that test is not satisfying. A probably better way is not to prevent a
connection from establishing if only BF_SHUTW_NOW is set but BF_SHUTW
is not. That way, the BF_SHUTW flag is not set if the request has any
data pending, which still fixes the stats issue, but does not let any
empty connection pass through.

Also, as a safety measure, we extend buffer_abort() to automatically
disable the BF_AUTO_CONNECT flag. While it appears to always be OK,
it is by pure luck, so better safe than sorry.
diff --git a/src/session.c b/src/session.c
index aa79457..34ffb11 100644
--- a/src/session.c
+++ b/src/session.c
@@ -1331,12 +1331,10 @@
 
 	/* first, let's check if the request buffer needs to shutdown(write), which may
 	 * happen either because the input is closed or because we want to force a close
-	 * once the server has begun to respond. Note that we only apply it once we're
-	 * connected, so that we still support queuing of a request with input already
-	 * closed.
+	 * once the server has begun to respond.
 	 */
 	if (unlikely((s->req->flags & (BF_SHUTW|BF_SHUTW_NOW|BF_HIJACK|BF_AUTO_CLOSE|BF_SHUTR)) ==
-		     (BF_AUTO_CLOSE|BF_SHUTR) && s->req->cons->state >= SI_ST_EST))
+		     (BF_AUTO_CLOSE|BF_SHUTR)))
 			buffer_shutw_now(s->req);
 
 	/* shutdown(write) pending */
@@ -1358,7 +1356,7 @@
 	 *  - the BF_AUTO_CONNECT flag is set (active connection)
 	 */
 	if (s->req->cons->state == SI_ST_INI) {
-		if (!(s->req->flags & (BF_SHUTW|BF_SHUTW_NOW))) {
+		if (!(s->req->flags & BF_SHUTW)) {
 			if ((s->req->flags & (BF_AUTO_CONNECT|BF_OUT_EMPTY)) != BF_OUT_EMPTY) {
 				/* If we have a ->connect method, we need to perform a connection request,
 				 * otherwise we immediately switch to the connected state.