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"