new attribute capacitystatus causes collisions.

Nobody has claimed this yet.

Since the release of : https://aws.amazon.com/about-aws/whats-new/2018/10/Amazon-EC2-now-offers-On-Demand-Capacity-Reservations/

For the ec2 products there is now a capacitystatus attribute that can be either UnusedCapacityReservation, AllocatedCapacityReservation or Used.

This is causing collisions and any products are being excluded from the pricing results. Here is an example of the three products that would collide on the hash "t2.medium|Linux|Shared|No License required|NA|US West (Oregon)"
```
{u'attributes': {u'capacitystatus': u'UnusedCapacityReservation',
u'clockSpeed': u'Up to 3.3 GHz',
u'currentGeneration': u'Yes',
u'ecu': u'Variable',
u'instanceFamily': u'General purpose',
u'instanceType': u't2.medium',
u'instancesku': u'2ES9C4RF3WGQZAQN',
u'licenseModel': u'No License required',
u'location': u'US West (Oregon)',
u'locationType': u'AWS Region',
u'memory': u'4 GiB',
u'networkPerformance': u'Low to Moderate',
u'normalizationSizeFactor': u'2',
u'operatingSystem': u'Linux',
u'operation': u'RunInstances',
u'physicalProcessor': u'Intel Xeon Family',
u'preInstalledSw': u'NA',
u'processorArchitecture': u'32-bit or 64-bit',
u'processorFeatures': u'Intel AVX; Intel Turbo',
u'servicecode': u'AmazonEC2',
u'servicename': u'Amazon Elastic Compute Cloud',
u'storage': u'EBS only',
u'tenancy': u'Shared',
u'usagetype': u'USW2-UnusedBox:t2.medium',
u'vcpu': u'2'},
u'productFamily': u'Compute Instance',
u'sku': u'EUSSFEHB68A6B6DM'}
{u'attributes': {u'capacitystatus': u'Used',
u'clockSpeed': u'Up to 3.3 GHz',
u'currentGeneration': u'Yes',
u'ecu': u'Variable',
u'instanceFamily': u'General purpose',
u'instanceType': u't2.medium',
u'licenseModel': u'No License required',
u'location': u'US West (Oregon)',
u'locationType': u'AWS Region',
u'memory': u'4 GiB',
u'networkPerformance': u'Low to Moderate',
u'normalizationSizeFactor': u'2',
u'operatingSystem': u'Linux',
u'operation': u'RunInstances',
u'physicalProcessor': u'Intel Xeon Family',
u'preInstalledSw': u'NA',
u'processorArchitecture': u'32-bit or 64-bit',
u'processorFeatures': u'Intel AVX; Intel Turbo',
u'servicecode': u'AmazonEC2',
u'servicename': u'Amazon Elastic Compute Cloud',
u'storage': u'EBS only',
u'tenancy': u'Shared',
u'usagetype': u'USW2-BoxUsage:t2.medium',
u'vcpu': u'2'},
u'productFamily': u'Compute Instance',
u'sku': u'2ES9C4RF3WGQZAQN'}
{u'attributes': {u'capacitystatus': u'AllocatedCapacityReservation',
u'clockSpeed': u'Up to 3.3 GHz',
u'currentGeneration': u'Yes',
u'ecu': u'Variable',
u'instanceFamily': u'General purpose',
u'instanceType': u't2.medium',
u'instancesku': u'2ES9C4RF3WGQZAQN',
u'licenseModel': u'No License required',
u'location': u'US West (Oregon)',
u'locationType': u'AWS Region',
u'memory': u'4 GiB',
u'networkPerformance': u'Low to Moderate',
u'normalizationSizeFactor': u'2',
u'operatingSystem': u'Linux',
u'operation': u'RunInstances',
u'physicalProcessor': u'Intel Xeon Family',
u'preInstalledSw': u'NA',
u'processorArchitecture': u'32-bit or 64-bit',
u'processorFeatures': u'Intel AVX; Intel Turbo',
u'servicecode': u'AmazonEC2',
u'servicename': u'Amazon Elastic Compute Cloud',
u'storage': u'EBS only',
u'tenancy': u'Shared',
u'usagetype': u'USW2-Reservation:t2.medium',
u'vcpu': u'2'},
u'productFamily': u'Compute Instance',
u'sku': u'J4QDBG6HHGV8ND4P'}
```
For the moment I am adding an additional filter to "def _generate_reverse_sku_mapping":
```
if product['attributes']['capacitystatus'] != 'Used':
continue
```
to get around the problem.

Start at _generate_reverse_sku_mapping and reproduce the collision using the three EC2 products shown in the issue. Trace how their attributes contribute to the reverse SKU mapping; done means the capacity-status variants no longer cause valid pricing products to be excluded or collide incorrectly.

Written by the indexing model from the issue text.