Copter: The failsafe enable flag should be cleared on cold reset

ArduCopter/failsafe.cpp

@@ -7,7 +7,7 @@
 //  our failsafe strategy is to detect main loop lockup and disarm the motors
 //
 
-static bool failsafe_enabled = false;
+static bool failsafe_enabled;
 static uint16_t failsafe_last_ticks;
 static uint32_t failsafe_last_timestamp;
 static bool in_failsafe;