Use "rtslib_fb" import instead of "rtslib"

[Eric Harney]

As of 2.1.52, rtslib_fb exports into its own namespace of "rtslib_fb" instead of "rtslib". We should migrate to using this in Cinder to be more clear about which version is tested/supported.

[John Griffith (john-griffith)]

Seems like a good idea

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/190099

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/190099
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=6532be7eda2c7eec2984d51f06f0c69311b7b572
Submitter: Jenkins
Branch: master

commit 6532be7eda2c7eec2984d51f06f0c69311b7b572
Author: Gorka Eguileor <email address hidden>
Date: Wed Jun 10 11:57:07 2015 +0200

    Use correct rtslib namespace for newer versions

    For rtslib-fb versions 2.1.52 and newer its own namespace (rtslib_fb) is
    recommended instead of the older one (rtslib).

    On versions with this new namespace a deprecation warning will be
    thrown: "'rtslib' package name for rtslib-fb is deprecated, please
    instead import 'rtslib_fb'"

    This patch uses this new namespace when possible and falls back to the
    older namespace if not.

    Change-Id: I984105458da4d7b8736bf7c83919cbe5feb9c85a
    Closes-Bug: #1460814