Refactor go-based test framework

[leonwanghui]

Signed-off-by: leonwanghui wanghui71leon@gmail.com

This PR contains huge refactor of current framework with these changes:

• Use openapi-generator instead of go-swagger tool to validate specification and generate golang code automatically
• Refactor both client and server module according new-born generated code
• Update all 3rd party vendor packages using dep tool
• Remove loose-check flag so as to check all test cases in Travis CI

@mattmcneeney @jberkhahn @fmui Please take a review at this PR, thanks!

[cfdreddbot]

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