Don't send helth check logs to the ES streaming lambda
Don't send helth check logs to the ES streaming lambda

Sets the filter pattern on the cloudwatch log subscriptions to
skip the health check requests.

The pattern has 2 parts:
* For nginx logs, log messages have a `.request` property, so we're
  checking that if the property is present it doesn't contain the
  status endpoint URL.
* For application logs, we're checking `url` instead.

alphagov/digitalmarketplace-aws,alphagov/digitalmarketplace-aws,alphagov/digitalmarketplace-aws