1) Added code to stop thread in aws_lambda.py & gcp.py.
2) Modified logic of run() function of class TimeoutThread to stop the thread and raise ServerlessTimeoutWarning exception, conditionally.

1) Improved the logic of run() function of class TimeoutThread to remove the dependency on time.sleep() method.

1) Removed CPU consuming while loop from logic of run method of TimeoutThread class.
2) Used Event class from threading module to send a stop signal for the thread.
3) Changed cancel() to stop() for stopping thread  for AWS and GCP integration files.

1) Replaced time.sleep() method with wait() method so that the thread terminates before completing the full waiting time.