Use HTTP_SUCCESS for checking success status code

rest_client contains HTTP_SUCCESS already for representing HTTP
success status codes and this patch replaces the status check with
it for the strict validation.

Change-Id: I70371883074addd4c76f08eced16e0b792247a5b
unskip test_integration_1

Finally the test_integration_1 test became unskipable.
* ssh a machine on neutron is not as flaky as before.
* Attaching volume to a booted instance is not flaky.
* EC2 Image bundle is working again.

Change-Id: I88dd708f1091d7d4ee1d7e03d800f7165f4936a4
TODO: Add stricter response validation.
Deduplicate negative test calls

Instead of duplicating the execute call for each negative test cases,
defining a generic way for all tests by registering a test function
dynamically on basis of the test class itself.

This is done using a class decorator (not inheritance) since it's
not possible to get the child class name on import time.

Change-Id: Ife0a8ea95ecfcac8a5f9c89babd74df0d5f884fe
Partially-implements: bp autogen-negative-tests
fix sahara base class

1. get client mamager after service available checking
2. checking cls's attribute in tearDownClass to avoid
   exceptions

Change-Id: I596284dceadcb5f0144495bd346d570c6bb35e0f
Split certificate API test

Test of certificate API was written as 1 test have 2 function tests.
There is no problem during it runs successfully.
But in case of failure, we cannot find easily about which part of function
was failed. It is not less preferred.
I split the test case as 1 test case checks 1 API.

Change-Id: I679394db42aad1e6e81bf3b023a69827aaf48d70
Merge "fix sahara base class"
Merge "Use HTTP_SUCCESS for checking success status code"
Merge "Deduplicate negative test calls"
Merge "unskip test_integration_1"
Merge "Split certificate API test"
Merge branch 'master' of https://github.com/openstack/tempest