standby switchover: display "shutdown_check_timeout" value in --dry-run mode

It's useful to be aware of this setting.

doc/switchover.xml

@@ -186,6 +186,7 @@
       NOTICE: local node "node2" (ID: 2) will be promoted to primary; current primary "node1" (ID: 1) will be demoted to standby
       INFO: following shutdown command would be run on node "node1":
         "pg_ctl -l /var/log/postgresql/startup.log -D '/var/lib/postgresql/data' -m fast -W stop"
+      INFO: parameter "shutdown_check_timeout" is set to 60 seconds
     </programlisting>
    </para>
 

repmgr-action-standby.c

@@ -4329,6 +4329,9 @@ do_standby_switchover(void)
 				 remote_node_record.node_name,
 				 shutdown_command);
 
+		log_info(_("parameter \"shutdown_check_timeout\" is set to %i seconds"),
+				 config_file_options.shutdown_check_timeout);
+
 		clear_node_info_list(&sibling_nodes);
 
 		key_value_list_free(&remote_config_files);