Use dummy share driver of manila with rally CI jobs

For the moment we use two different share back ends for two existing
Rally CI jobs that run against manila project. It is redundant, as in
case of CI we intend to test main manila functionality, that is
back end agnostic. So, switch them to 'dummy' share driver and
disable all other redundant services, that also will reduce deployment
time.

Change-Id: I753a648349f7a3b8ede3ee714657638f4db68ec5

jenkins/jobs/rally.yaml

@@ -218,6 +218,11 @@
           #!/bin/bash -xe
           export PROJECTS="openstack/python-manilaclient openstack/rally $PROJECTS"
 
+          # Run only manila services, because only main manila functionality
+          # will be tested with 'dummy' share driver that does not use real
+          # storage back ends. Also, it will speed up devstack installation.
+          export OVERRIDE_ENABLED_SERVICES=key,mysql,rabbit
+
           export IDENTITY_API_VERSION=3
 
           export DEVSTACK_GATE_NEUTRON=1
@@ -263,7 +268,7 @@
       - devstack-manila-rally-gate-multibackend:
           scenario: 'rally-manila'
           dhss: '1'
-          driver: 'generic'
+          driver: 'dummy'
 
     publishers:
       - devstack-logs
@@ -284,7 +289,7 @@
       - devstack-manila-rally-gate-multibackend:
           scenario: 'rally-manila-no-ss'
           dhss: '0'
-          driver: 'zfsonlinux'
+          driver: 'dummy'
 
     publishers:
       - devstack-logs