Pin barbican-tempest-plugin for jobs in EM

Let's pin barbican-tempest-plugin for jobs that run code from branches in extended maintenance.

This change is required because these jobs install older version of tempest that does not contain all functions consumed by master barbicna-tempest-plugin.

Change-Id: Ia4a30d12de1a58b93a06979188e662edeef21ec6
1 file changed