Resets an attribute of an instance to its default value. To reset the
kernel or ramdisk, the instance must be in a stopped state. To reset
the sourceDestCheck, the instance can be either running or stopped.
The sourceDestCheck attribute controls whether source/destination
checking is enabled. The default value is true, which means checking
is enabled. This value must be false for a NAT instance to perform
NAT. For more information, see NAT Instances
in the Amazon Virtual Private Cloud User Guide.