Propose osb-checker go-based test framework

[leonwanghui]

Hi all, here is the initial version of test framework, though it's not finished yet, but users can just try to test it in their development pipelines.

Design

For design details, please refer to here

Test

• Firstly, u need to deploy your own service broker to be tested.
• Modify the config_mock.yaml under test/configs folder.
• Just run go test -v ./test/ to start the test job.

Generate model

All the model will be generated from swagger.yaml automatically. Here are some steps for developers to generate the model:

• First developers should download go-swagger tool from here
• Then run these command below:

  cd ./autogenerated && wget https://raw.githubusercontent.com/openservicebrokerapi/servicebroker/master/swagger.yaml
  go-swagger generate model ./swagger.yaml

[cfdreddbot]

:white_check_mark: Hey leonwanghui! The commit authors and yourself have already signed the CLA.

[leonwanghui]

@fmui @mattmcneeney Any comments or concerns on this PR?

[mattmcneeney]

I haven't actually tried it and can't review the code, but happy for you to make the call if others are happy!