XenAPI:  Find location for XenAPI plugins

Plugins can be installed in different places in dom0; re-enable the
use of xapi_plugin_location

Change-Id: If94ec6b250ad5b4f7730cfbf443d937eb85feb5c
cinder_driver_certs.sh always passes driver

In cinder_driver_certs.sh, the tests are run and output is
piped to "tee".  Currently, checking the exit code of this
command only checks that "tee" exited properly.  Using the
pipefail option for this script will ensure the entire
pipe succeeds before passing a driver.

Change-Id: I58311aa0e2c779467d39c4477c4ea39d14eda207
Closes-Bug: #1289129
Merge "cinder_driver_certs.sh always passes driver"
Merge "XenAPI:  Find location for XenAPI plugins"
Merge branch 'master' of github.com:openstack-dev/devstack