Add the concurrent rollback integration test.
Add the concurrent rollback integration test.

Change-Id: Iaa4e290326e6910ddcf6abe6674ba499a49ec19e

cloudfoundry-incubator/bosh-vcloud-cpi-release,wcamarao/bosh-vcloud-cpi-release,cloudfoundry-incubator/bosh-vcloud-cpi-release,wcamarao/bosh-vcloud-cpi-release,cloudfoundry-incubator/bosh-vcloud-cpi-release,wcamarao/bosh-vcloud-cpi-release