Fix Clang static analyzer warnings about never read values

cmdmon.c

@@ -1937,8 +1937,6 @@ read_from_cmd_socket(void *anything)
     /* This should be already handled */
     assert(0);
   } else {
-    allowed = 0;
-
     /* Check level of authority required to issue the command */
     switch(permissions[rx_command]) {
       case PERMIT_AUTH:
@@ -1960,6 +1958,7 @@ read_from_cmd_socket(void *anything)
         break;
       default:
         assert(0);
+        allowed = 0;
     }
 
     if (allowed) {

ntp_core.c

@@ -1548,6 +1548,8 @@ NCR_SlewTimes(NCR_Instance inst, struct timeval *when, double dfreq, double doff
 #ifdef TRACEON
   LOG(LOGS_INFO, LOGF_NtpCore, "rx prev=[%s] new=[%s]",
       UTI_TimevalToString(&prev), UTI_TimevalToString(&inst->local_rx));
+#else
+  (void)prev;
 #endif
   prev = inst->local_tx;
   if (inst->local_tx.tv_sec || inst->local_tx.tv_usec)

sourcestats.c

@@ -631,7 +631,7 @@ SST_SlewSamples(SST_Stats inst, struct timeval *when, double dfreq, double doffs
         i, UTI_TimevalToString(&prev), UTI_TimevalToString(sample),
         prev_offset, inst->offsets[i]);
 #else
-    (void)prev_offset;
+    (void)prev; (void)prev_offset;
 #endif
   }
 
@@ -650,7 +650,7 @@ SST_SlewSamples(SST_Stats inst, struct timeval *when, double dfreq, double doffs
       prev_offset, inst->estimated_offset,
       1.0e6*prev_freq, 1.0e6*inst->estimated_frequency);
 #else
-  (void)prev; (void)prev_freq;
+  (void)prev; (void)prev_offset; (void)prev_freq;
 #endif
 }