Add calls to InitError and ExitError to notify the lambda runtime that the extension had an error

[estolfo]

See the documentation here for InitError and ExitError https://docs.aws.amazon.com/lambda/latest/dg/runtimes-extensions-api.html

We currently don't notify the lambda runtime if the extension encounters an error and we want the runtime to stop further API calls. We might not actually want to do this but we should research and make a decision.