MINOR: tree-wide: Replace several chn_cons() by the corresponding SC

At many places, call to chn_cons() can be easily replaced by the
corresponding SC. It is a bit easier to understand which side is
manipulated.
diff --git a/src/stream.c b/src/stream.c
index 83e3b72..9c3361f 100644
--- a/src/stream.c
+++ b/src/stream.c
@@ -1956,7 +1956,7 @@
 	if (((req->flags & ~rqf_last) & CF_MASK_ANALYSER) ||
 	    ((scf->flags ^ scf_flags) & (SC_FL_ABRT_DONE|SC_FL_ABRT_WANTED)) ||
 	    ((scb->flags ^ scb_flags) & (SC_FL_SHUT_DONE|SC_FL_SHUT_WANTED)) ||
-	    (req->analysers && (chn_cons(req)->flags & SC_FL_SHUT_DONE)) ||
+	    (req->analysers && (scb->flags & SC_FL_SHUT_DONE)) ||
 	    scf->state != rq_prod_last ||
 	    scb->state != rq_cons_last ||
 	    s->pending_events & TASK_WOKEN_MSG) {
@@ -2061,7 +2061,7 @@
 	if (((res->flags & ~rpf_last) & CF_MASK_ANALYSER) ||
 	    ((scb->flags ^ scb_flags) & (SC_FL_ABRT_DONE|SC_FL_ABRT_WANTED)) ||
 	    ((scf->flags ^ scf_flags) & (SC_FL_SHUT_DONE|SC_FL_SHUT_WANTED)) ||
-	    (res->analysers && (chn_cons(res)->flags & SC_FL_SHUT_DONE)) ||
+	    (res->analysers && (scf->flags & SC_FL_SHUT_DONE)) ||
 	    scf->state != rp_cons_last ||
 	    scb->state != rp_prod_last ||
 	    s->pending_events & TASK_WOKEN_MSG) {