cpg: do_proc_join change list_slice to list_add

In this concrete case result is equivalent but makes coverity happy.

Signed-off-by: Jan Friesse <jfriesse@redhat.com>
Reviewed-by: Steven Dake <sdake@redhat.com>

services/cpg.c

@@ -1009,7 +1009,7 @@ static void do_proc_join(
 		}
 		list_to_add = list;
 	}
-	list_splice (&pi->list, list_to_add);
+	list_add (&pi->list, list_to_add);
 
 	notify_info.pid = pi->pid;
 	notify_info.nodeid = nodeid;