fix: coverity issues

source/os/src/osTimezone.c

@@ -745,8 +745,7 @@ void taosSetSystemTimezone(const char *inTimezoneStr, char *outTimezoneStr, int8
   if (inTimezoneStr == NULL || inTimezoneStr[0] == 0) return;
 
   size_t len = strlen(inTimezoneStr);
-  char *buf = taosMemoryMalloc(len + 1);
-  memset(buf, 0, len + 1)
+  char  *buf = taosMemoryCalloc(len + 1, 1);
   for (int32_t i = 0; i < len; i++) {
     if (inTimezoneStr[i] == ' ' || inTimezoneStr[i] == '(') {
       buf[i] = 0;