RDS Default StorageType is magnetic

[aarcro]

As an RDS user
I'd like to get io1 or gp2 disks depending on if iops is declared
So that I don't use slow spinning disks

Current:
When StorageType is not set, and iops == 0, magnetic disks are provisioned

Expected:
When StorageType is not set, and iops == 0, gp2 SSD disks are provisioned

I'm guessing this is RDS default behavior for Ref("AWS::NoValue") I'd recommend using something like StorageType = variables['StorageType'] or 'io1' if get_piops() > 0 else 'gp2'