I ran rally test on mos 5.1.1 and 6.0, just modified few options in rally scenario:
 - to_flavor "tiny" - compute modes has only 3Gb RAM
 - image name "TestVM"
 - times: 3

 (.venv)developer@nailgun:stack$ cat ./rally/doc/samples/tasks/scenarios/nova/resize-server.yaml
---
  NovaServers.resize_server:
    -
      args:
        flavor:
            name: "m1.nano"
        image:
            name: "TestVM"
        to_flavor:
            name: "m1.tiny"
        confirm: true
        force_delete: false
      runner:
        type: "constant"
        times: 3
        concurrency: 5
      context:
        users:
          tenants: 1
          users_per_tenant: 1

(.venv)developer@nailgun:stack$ fuel --f
api: '1.0'
astute_sha: 16b252d93be6aaa73030b8100cf8c5ca6a970a91
auth_required: true
build_id: 2014-12-18_01-32-01
build_number: '56'
feature_groups:
- mirantis
fuellib_sha: 73332192a257ea02c40a39885c502ad1ebdf3eda
fuelmain_sha: 45caacadb878abfbd9d60e134d72229698b469c9
nailgun_sha: 5f91157daa6798ff522ca9f6d34e7e135f150a90
ostf_sha: a9afb68710d809570460c29d6c3293219d3624d4
production: docker
release: '6.0'
release_versions:
  2014.2-6.0:
    VERSION:
      api: '1.0'
      astute_sha: 16b252d93be6aaa73030b8100cf8c5ca6a970a91
      build_id: 2014-12-18_01-32-01
      build_number: '56'
      feature_groups:
      - mirantis
      fuellib_sha: 73332192a257ea02c40a39885c502ad1ebdf3eda
      fuelmain_sha: 45caacadb878abfbd9d60e134d72229698b469c9
      nailgun_sha: 5f91157daa6798ff522ca9f6d34e7e135f150a90
      ostf_sha: a9afb68710d809570460c29d6c3293219d3624d4
      production: docker
      release: '6.0'

 (.venv)developer@nailgun:stack$ rally-runner ./rally/doc/samples/tasks/scenarios/nova/resize-server.yaml
Start 'tail -f /var/log/rally/rally.log' for logs
..rally.doc.samples.tasks.scenarios.nova
    resize-server [3 iterations, 5 threads]                             OK  249.19


Ran 1 test in 320.414s

OK
tar: Removing leading `/' from member names

----

(.venv)developer@nailgun:stack$ fuel --f
api: '1.0'
astute_sha: dade74af41d4972fe05a1c16ae1db2a2e60c6715
auth_required: true
build_id: 2014-11-23_21-01-00
build_number: '34'
feature_groups:
- mirantis
fuellib_sha: 444339cae21c369c1d95e96c1059d4099077138e
fuelmain_sha: 0fe3db7475b9f8b287c5b59cba94c9a40a8d8101
nailgun_sha: 7580f6341a726c2019f880ae23ff3f1c581fd850
ostf_sha: 64cb59c681658a7a55cc2c09d079072a41beb346
production: docker
release: 5.1.1
release_versions:
  2014.1.3-5.1.1:
    VERSION:
      api: '1.0'
      astute_sha: dade74af41d4972fe05a1c16ae1db2a2e60c6715
      build_id: 2014-11-23_21-01-00
      build_number: '34'
      feature_groups:
      - mirantis
      fuellib_sha: 444339cae21c369c1d95e96c1059d4099077138e
      fuelmain_sha: 0fe3db7475b9f8b287c5b59cba94c9a40a8d8101
      nailgun_sha: 7580f6341a726c2019f880ae23ff3f1c581fd850
      ostf_sha: 64cb59c681658a7a55cc2c09d079072a41beb346
      production: docker
      release: 5.1.1

(.venv)developer@nailgun:stack$ rally-runner ./rally/doc/samples/tasks/scenarios/nova/resize-server.yaml
Start 'tail -f /var/log/rally/rally.log' for logs
..rally.doc.samples.tasks.scenarios.nova
    resize-server [3 iterations, 5 threads]                             OK  227.06


Ran 1 test in 299.214s

OK
tar: Removing leading `/' from member names