LOG: do not depend on oai_exit

By using oai_exit in log.c, LOG depends on being compiled into an
executable that defines such symbol, which is not always the case (nor
does it make sense).

oai_exit is only used in a loop to optionally write out memory. The
loop could relatively easily be aborted by setting a variable:

common/utils/LOG/log.c

@@ -45,6 +45,7 @@
 #include "common/config/config_userapi.h"
 #include <time.h>
 #include <sys/time.h>
+#include <stdatomic.h>
 #include "common/utils/LOG/log_extern.h"
 
 // main log variables
@@ -810,7 +811,7 @@ void logClean (void)
   }
 }
 
-extern int oai_exit;
+static atomic_bool stop_flush_mem_to_file = false;
 void flush_mem_to_file(void)
 {
   int fp;
@@ -821,7 +822,7 @@ void flush_mem_to_file(void)
   
   pthread_setname_np( pthread_self(), "flush_mem_to_file");
 
-  while (!oai_exit) {
+  while (!atomic_load(&stop_flush_mem_to_file)) {
     pthread_mutex_lock(&log_mem_lock);
     log_mem_write_flag=0;
     pthread_cond_wait(&log_mem_notify, &log_mem_lock);
@@ -981,6 +982,7 @@ void close_log_mem(void){
   char f_name[1024];
 
   if(log_mem_flag==1){
+    atomic_store(&stop_flush_mem_to_file, false);
     log_mem_d[0].enable_flag=0;
     log_mem_d[1].enable_flag=0;
     usleep(10); // wait for log writing