Dynamo threshold calculation does not take into account period

[tomhaigh]

It assumes it's the sum over 1 minute https://github.com/justeat/AwsWatchman/blob/1cd80b44135569b0623d3891f3214ec667b936a6/Watchman.AwsResources/Services/DynamoDb/DynamoDbDataProvider.cs#L54 but the number of periods can be overriden in config