Replay: don't write out duplicate FMT messages

this makes replay output the same as input for when input is a replay
log

Tools/Replay/DataFlashFileReader.cpp

@@ -6,8 +6,6 @@
 #include <stdio.h>
 #include <unistd.h>
 
-DataFlashFileReader::DataFlashFileReader() : fd(-1) {}
-
 bool DataFlashFileReader::open_log(const char *logfile)
 {
     fd = ::open(logfile, O_RDONLY);
@@ -41,6 +39,11 @@ bool DataFlashFileReader::update(char type[5])
         return handle_log_format_msg(f);
     }
 
+    if (!done_format_msgs) {
+        done_format_msgs = true;
+        end_format_msgs();
+    }
+
     const struct log_Format &f = formats[hdr[2]];
     if (f.length == 0) {
         // can't just throw these away as the format specifies the