Drop extra listen() call in gss-server

There is already call to listen in create_socket(), and there is no
need to tie the backlog to the number of threads.  Also, here listen()
was sometimes called with zero backlog, making gss-server execution
(and tests) racy on slower and busy systems.

src/appl/gss-sample/gss-server.c

@@ -766,8 +766,6 @@ main(int argc, char **argv)
         int     stmp;
 
         if ((stmp = create_socket(port)) >= 0) {
-            if (listen(stmp, max_threads == 1 ? 0 : max_threads) < 0)
-                perror("listening on socket");
             fprintf(stderr, "starting...\n");
 
             do {

src/tests/gss-threads/gss-server.c

@@ -782,9 +782,6 @@ main(int argc, char **argv)
 
         stmp = create_socket(port);
         if (stmp >= 0) {
-            if (listen(stmp, max_threads == 1 ? 0 : max_threads) < 0)
-                perror("listening on socket");
-
             do {
                 struct _work_plan * work = malloc(sizeof(struct _work_plan));