Add code and comment about resetting watchdog.

Which is needed if the bootloader will be invoked by the
sketch as a service ('J' command.)

optiboot/examples/test_reset/test_reset.ino

@@ -78,6 +78,16 @@ void printReset(const char *label, uint8_t resetFlags)
 }
 
 void setup() {
+#if 1
+  /*
+   * if we're going to allow the bootloader to be called as a service ('j" command),
+   * then we need to disable the WDT when the sketch starts.  Essentially, there is no
+   * way to tell a watchdog that occurs during the sketch from the watchdog that will
+   * re-start the sketch when the bootloader is called from the application.
+   */
+  MCUSR = ~(1 << WDRF); // allow us to disable WD
+  wdt_disable();
+#endif
   Serial.begin(9600);  // Initialize serial port
 
   Serial.println(F("Reset flag test\n"));