Make spot product description config

[russellballestrini]

Issue Type

• Feature Pull Request
• Documentation Pull Request

Summary

The Linux/UNIX product description does not have the price history for the most recent 2 instance type generations, as proved here: http://pad.yohdah.com/598/spot-product-no-history

As a result we have decided to change the default SpotProductDescription to Linux/UNIX (Amazon VPC) as well as make it configurable for backwards compatibility reasons (and so that we can support other operating systems like Windows, etc.)

• Changes the default Spot Product Description from Linux/UNIX to Linux/UNIX (Amazon VPC)
• Adds a flag to allow configuration of -spot_product_description
• Updates CLI help text for readability
• Derives flag defaults from constants

Code contribution checklist

1. The contribution fixes a single existing github issue, and it is linked
   to it.

Might fix the following: #206 #213

1. The code is as simple as possible, readable and follows the idiomatic Go
   guidelines.

2. All new functionality is covered by automated test cases so the overall
   test coverage doesn't decrease.

3. No issues are reported when running make full-test.

This doesn't work on Mac but I'm pretty but I ran go fmt and go test

1. Functionality not applicable to all users should be configurable.
2. Configurations should be exposed through Lambda function environment
   variables which are also passed as parameters to the
   CloudFormation
   and
   Terraform
   stacks defined as infrastructure code.
3. Global configurations set from the infrastructure stack level should also
   support per-group overrides using tags.
4. Tags names and expected values should be similar to the other existing
   configurations.
5. Both global and tag-based configuration mechanisms should be tested and
   proven to work using log output from various test runs.
6. The logs should be kept as clean as possible (use log levels as
   appropriate) and formatted consistently to the existing log output.
7. The documentation is updated to cover the new behavior, as well as the
   new configuration options for both stack parameters and tag overrides.
8. A code reviewer reproduced the problem and can confirm the code
   contribution actually resolves it.

[cristim]

LGTM, once exposed to Terraform and CloudFormation!

@xlr-8 do you have any comments?

[coveralls]

Coverage increased (+0.1%) to 74.076% when pulling b152168 on russellballestrini:make-spot-product-description-config into 4894cb6 on cristim:master.

[xlr-8]

I would have simply added a small check as we have the "valid values" in order to ensure it's included, or fallback on the default one. I can open an issue if you think this is relevant