MEDIUM: session: Steal owner-less connections on end of transaction.

When a transaction ends, if we want to do keepalive, and the connection we
used didn't have an owner, attach the connection to the session, so that we
don't have to destroy it, and we can reuse it later.
diff --git a/src/proto_http.c b/src/proto_http.c
index eb898a7..7c658d9 100644
--- a/src/proto_http.c
+++ b/src/proto_http.c
@@ -70,6 +70,7 @@
 #include <proto/queue.h>
 #include <proto/sample.h>
 #include <proto/server.h>
+#include <proto/session.h>
 #include <proto/stream.h>
 #include <proto/stream_interface.h>
 #include <proto/task.h>
@@ -3748,10 +3749,6 @@
 
 	/* unless we're doing keep-alive, we want to quickly close the connection
 	 * to the server.
-	 * XXX cognet: If the connection doesn't have a owner then it may not
-	 * be referenced  anywhere, just kill it now, even if it could be reused.
-	 * To be revisited later when revisited later when we handle connection
-	 * pools properly.
 	 */
 	if (((s->txn->flags & TX_CON_WANT_MSK) != TX_CON_WANT_KAL) ||
 	    !si_conn_ready(&s->si[1]) || !srv_conn->owner) {
@@ -3842,8 +3839,12 @@
 	 * We then can call si_release_endpoint() to destroy the conn_stream
 	 */
 	if (((s->txn->flags & TX_CON_WANT_MSK) != TX_CON_WANT_KAL) ||
-	    !si_conn_ready(&s->si[1]) || !srv_conn->owner)
+	    !si_conn_ready(&s->si[1]))
 		srv_conn = NULL;
+	else if (!srv_conn->owner) {
+		srv_conn->owner = s->sess;
+		session_add_conn(s->sess, srv_conn, s->target);
+	}
 	si_release_endpoint(&s->si[1]);
 
 	s->si[1].state     = s->si[1].prev_state = SI_ST_INI;