patch 7.4.1413
Problem:    When calling ch_close() the close callback is invoked, even though
            the docs say it isn't. (Christian J. Robinson)
Solution:   Don't call the close callback.
diff --git a/src/eval.c b/src/eval.c
index b04b6c2..db9c6b7 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -10213,7 +10213,7 @@
     channel_T *channel = get_channel_arg(&argvars[0]);
 
     if (channel != NULL)
-	channel_close(channel);
+	channel_close(channel, FALSE);
 }
 
 # ifdef FEAT_JOB