Remove Resp status code checks in stress tests

As response code checks is done at client side,
tests case do not need to check the same again.

This patch removes status code checks in stress tests.
All removed status code checks are present on client side.

Partially Implements blueprint: client-checks-success

Change-Id: I1f09b25d6d6d1c966a0635509d670c55d9415468
Remove setUpClass added after cleanup

After the cleanup of setUpClass a new one managed to sneak
in. Removing it now, and enforcing the hacking rule in next
patchset.

Change-Id: If53b3a7d299f01f7c45739f5b2f023fbdb73aa45
Merge "Remove Resp status code checks in stress tests"
Merge "Remove setUpClass added after cleanup"
Merge branch 'master' of https://github.com/openstack/tempest