Add more possible reboot causes

Author: jleveque

sonic_platform_base/chassis_base.py

@@ -23,6 +23,8 @@ class ChassisBase(device_base.DeviceBase):
     # Possible reboot causes
     REBOOT_CAUSE_POWER_LOSS = "power_loss" 
     REBOOT_CAUSE_THERMAL_OVERLOAD = "thermal_overload"
+    REBOOT_CAUSE_INSUFFICIENT_FAN = "insufficient_fan"
+    REBOOT_CAUSE_WATCHDOG = "watchdog"
     REBOOT_CAUSE_SOFTWARE = "software"
 
     # List of all fans available on the chassis