sys: avoid syslog message when leap bits are not changed

After leap second the kernel removes STA_INS and STA_DEL bits from the
adjtimex status automatically, don't report a change when clearing the
bits.

sys_linux.c

@@ -174,6 +174,15 @@ read_frequency(void)
 static void
 set_leap(int leap)
 {
+  int current_leap;
+
+  if (TMX_GetLeap(&current_leap) < 0) {
+    LOG_FATAL(LOGF_SysLinux, "adjtimex() failed in set_leap");
+  }
+
+  if (current_leap == leap)
+    return;
+
   if (TMX_SetLeap(leap) < 0) {
     LOG_FATAL(LOGF_SysLinux, "adjtimex() failed in set_leap");
   }

wrap_adjtimex.c

@@ -123,6 +123,28 @@ TMX_SetLeap(int leap)
   return adjtimex(&txc);
 }
 
+int
+TMX_GetLeap(int *leap)
+{
+  struct timex txc;
+
+  txc.modes = 0;
+  if (adjtimex(&txc) < 0)
+    return -1;
+
+  status &= ~(STA_INS | STA_DEL);
+  status |= txc.status & (STA_INS | STA_DEL);
+
+  if (status & STA_INS)
+    *leap = 1;
+  else if (status & STA_DEL)
+    *leap = -1;
+  else
+    *leap = 0;
+
+  return 0;
+}
+
 int TMX_SetSync(int sync, double est_error, double max_error)
 {
   struct timex txc;

wrap_adjtimex.h

@@ -31,6 +31,7 @@ int TMX_ResetOffset(void);
 int TMX_SetFrequency(double *freq, long tick);
 int TMX_GetFrequency(double *freq, long *tick);
 int TMX_SetLeap(int leap);
+int TMX_GetLeap(int *leap);
 int TMX_SetSync(int sync, double est_error, double max_error);
 int TMX_TestStepOffset(void);
 int TMX_ApplyStepOffset(double offset);