logging: disable all debug messages in non-debug build

For consistency, don't print debug messages that are compiled in due to
using the LOG macro instead of DEBUG_LOG.

client.c

@@ -3208,7 +3208,9 @@ main(int argc, char **argv)
         csv_mode = 1;
         break;
       case 'd':
+#if DEBUG > 0
         log_min_severity = LOGS_DEBUG;
+#endif
         break;
       case 'h':
         hostnames = optarg;

logging.c

@@ -214,7 +214,8 @@ LOG_OpenSystemLog(void)
 
 void LOG_SetMinSeverity(LOG_Severity severity)
 {
-  log_min_severity = CLAMP(LOGS_DEBUG, severity, LOGS_FATAL);
+  /* Don't print any debug messages in a non-debug build */
+  log_min_severity = CLAMP(DEBUG > 0 ? LOGS_DEBUG : LOGS_INFO, severity, LOGS_FATAL);
 }
 
 /* ================================================== */