fix: redeploy api if the openapi version changes

[praneetap]

Issue #, if available:
#191
Description of changes:
If the template has OpenApiVersion flag defined, change the hash generated so the api gets redeployed.
Description of how you validated changes:
First I deployed a simple hello world template.

Globals:
  Function:
    Timeout: 3

Resources:
  HelloWorldFunction:
    Type: AWS::Serverless::Function
    Properties:
      InlineCode: |
        exports.handler = async (event) => {
          const response = {
            statusCode: 200,
            body: JSON.stringify('Hello from Lambda!'),
          };
          return response;
        };      
      Handler: index.handler
      Runtime: nodejs8.10
      Events:
        HelloWorld:
          Type: Api 
          Properties:
            Path: /hello
            Method: get

Outputs:
  HelloWorldApi:
    Description: "API Gateway endpoint URL for Prod stage for Hello World function"
    Value: !Sub "https://${ServerlessRestApi}.execute-api.${AWS::Region}.amazonaws.com/Prod/hello/"
  HelloWorldFunction:
    Description: "Hello World Lambda Function ARN"
    Value: !GetAtt HelloWorldFunction.Arn
  HelloWorldFunctionIamRole:
    Description: "Implicit IAM Role created for Hello World function"
    Value: !GetAtt HelloWorldFunctionRole.Arn

Then I added the OpenApiVersion flag to the template with version '2.0', which wouldnt change the swagger document from the template above.

Globals:
  Function:
    Timeout: 3
  Api:
    OpenApiVersion: "2.0"

Resources:
  HelloWorldFunction:
    Type: AWS::Serverless::Function
    Properties:
      InlineCode: |
        exports.handler = async (event) => {
          const response = {
            statusCode: 200,
            body: JSON.stringify('Hello from Lambda!'),
          };
          return response;
        };      
      Handler: index.handler
      Runtime: nodejs8.10
      Events:
        HelloWorld:
          Type: Api
          Properties:
            Path: /hello
            Method: get

Outputs:
  HelloWorldApi:
    Description: "API Gateway endpoint URL for Prod stage for Hello World function"
    Value: !Sub "https://${ServerlessRestApi}.execute-api.${AWS::Region}.amazonaws.com/Prod/hello/"
  HelloWorldFunction:
    Description: "Hello World Lambda Function ARN"
    Value: !GetAtt HelloWorldFunction.Arn
  HelloWorldFunctionIamRole:
    Description: "Implicit IAM Role created for Hello World function"
    Value: !GetAtt HelloWorldFunctionRole.Arn

I verified that the API got redeployed by looking at the deployment history on API GW console.
The API gateway Stage stage was on the older deployment version than Prod stage.

Checklist:

• Write/update tests
• make pr passes
• Update documentation
• Verify transformed template deploys and application functions as expected
• Add/update example to examples/2016-10-31

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-io]

Codecov Report

Merging #1056 into develop will increase coverage by <.01%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           develop    #1056      +/-   ##
===========================================
+ Coverage    94.92%   94.92%   +<.01%     
===========================================
  Files           69       69              
  Lines         3250     3253       +3     
  Branches       632      633       +1     
===========================================
+ Hits          3085     3088       +3     
  Misses          87       87              
  Partials        78       78

Impacted Files	Coverage Δ
samtranslator/model/api/api_generator.py	96.64% <100%> (ø)	⬆️
samtranslator/model/apigateway.py	97.76% <100%> (+0.03%)	⬆️

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[jlhood]

Thanks for fixing this!