Add support for negative tests with admin client

This adds the missing support for admin clients and implements an
example based on flavor creation. Instead of listing all result code
checks it is now possible to define on default.

Change-Id: I9512c1b91eb227e35faf24e3e88ed73a6ed3b734
Partially-implements: bp autogen-negative-tests
Add ignore files related to coverage to .gitignore

.coverage and cover are generated by tox's cover task. So we should
ignore them.

Change-Id: Ica14d566fcd7bd31fea87471178db882add7813a
Add shelve_offload test for Nova API

On compute nodes which are configured with shelved_offload_time = -1,
the shelve API changes a server status to SHELVED and a server image
remains in the node. The shelve_offload API offloads the server image
from the node. This patch adds the API test for Nova API.

Partially implements blueprint nova-v3-api-tests

Change-Id: Iaa2f94c3381c8b68df7fe132e1c13b4b81962b8c
Verify more information in API tests for LBaaS

In API tests for LBaaS not all information is checked  that is
required.
For example, test_show_* checks only equality of name and id;
test_associate_disassociate_health_monitor_with_pool does not check
that pool containts healthmonitor after assosiating.

This tests should be corrected.

Also create_member and update_member was updated to use _create and
_update from network_client_base.

Closes-bug: #1262112

Change-Id: I352253ce9e28b46324a81e40c6b86759e0687420
Merge "Verify more information in API tests for LBaaS"
Merge "Add ignore files related to coverage to .gitignore"
Merge "Add support for negative tests with admin client"
Merge "Add shelve_offload test for Nova API"
Merge branch 'master' of https://github.com/openstack/tempest