Draft: pthread_create, RT scheduler, and address sanitizer are incompatible in Ubuntu 18.04

When we run with the RT scheduler and the address sanitizer in Ubuntu 18.04, pthread_create will hang and never create threads. This MR adds a warning such that other users are informed about this issue

common/utils/telnetsrv/telnetsrv.c

@@ -142,7 +142,7 @@ void set_sched(pthread_t tid, int pid, int priority) {
     schedp.sched_priority= NICE_MIN - priority ;
 
     if (   (schedp.sched_priority < sched_get_priority_min(SCHED_FIFO)) ||
-          (schedp.sched_priority > sched_get_priority_max(SCHED_FIFO)) ) {
+           (schedp.sched_priority > sched_get_priority_max(SCHED_FIFO)) ) {
       client_printf("Error: %i invalid prio, should be %i to %i, \n",
                     priority, NICE_MIN -sched_get_priority_min(SCHED_FIFO),
                     NICE_MIN - sched_get_priority_max(SCHED_FIFO) );