Disable task cache for worker lambdas by default, improve logging

[twelch]

Workers caching their task results increases the number of dynamodb items per report run by significantly. If 1 gp function splits its work over 5 workers, then there's 5 times as many dynamodb items. The current assumption is that the parent gp function will cache their results, and therefore the worker results don't need to be cached. This will cut down on the amount of dynamodb writes.

Requirements

• Give runLambdaWorker caller control over whether caching or not. Defaults to not cache. Can be turned on for debugging purposes.

ToDo:

• Add disableServerCache option to geoprocessing handler request and task model
• Switch to default to not cache
• refactor task.create to use options object