DynamoDB Global index capacity read from AWS is not used

[ghost]

The throughput value for a global secondary index read from the actual AWS table is never read, and always defaults to 5.

The following code needs to be added to table.py inside _introspect_all_indexes.
if 'ProvisionedThroughput' in field:
raw_throughput = field['ProvisionedThroughput']
kwargs['throughput'] = {}
kwargs['throughput']['read'] = int(raw_throughput['ReadCapacityUnits'])
kwargs['throughput']['write'] = int(raw_throughput['WriteCapacityUnits'])

[ferrants]

I am running into this as well. I've been able to track the issue to these lines:
https://github.com/boto/boto/blob/master/boto/dynamodb2/fields.py#L222
https://github.com/boto/boto/blob/master/boto/dynamodb2/table.py#L110

@mballou11 I implemented your suggestion here. #3447