Cinder client does not honor disable_ssl_certificate_validation

The Client() class should pass in insecure as the value of
CONF.identity.disable_ssl_certificate_validation, otherwise many
tests will fail if the cinder server is secured with SSL.

Change-Id: I9bb6ff48a0d53b5b124e58c9959c9a43da8c7e5c
Closes-Bug: 1298019
Stop neutron resource leaking even if an error occurs

In some test, if an error occurs in setUpClass(), some resources
are not deleted because of tearDownClass() is not called.
This commit fixes it.

 tempest/api
  +---- baremetal (unnecessary)
  +---- compute
  +---- data_processing (unnecessary)
  +---- database (unnecessary)
  +---- identity
  +---- image (done)
  +---- network         <-- this patch
  +---- object_storage
  +---- orchestration
  +---- queuing (unnecessary)
  +---- telemetry (unnecessary)
  +---- volume (done)

Partially Implements: blueprint stop-leaking

Change-Id: I580be8f974e3daa8ae4895ebb3e4311be8f9c242
Merge "Cinder client does not honor disable_ssl_certificate_validation"
Merge "Stop neutron resource leaking even if an error occurs"
Merge branch 'master' of https://github.com/openstack/tempest