storpool driver does a blind import of libs that don't exist on system

[John Griffith]

storpool it seems has it's own libs that it imports in it's driver, unfortunately there's no requirement for these libs so the import fails if it's hit.

Wrap a try_import around these like we do with other third party driver libs.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/143570

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/143570
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=84431839d972a9a2339ee220e3183130cd47c11c
Submitter: Jenkins
Branch: master

commit 84431839d972a9a2339ee220e3183130cd47c11c
Author: John Griffith <email address hidden>
Date: Mon Dec 22 17:05:01 2014 -0700

    Fix broken StorPool driver

    The newly added StorPool driver has a number of issues;
    It imports it's own 3'rd party libs which are not in the
    requirements file, it declares conf options but never registers
    them, and as a result of these two things it break the ability
    to generate a configuration file.

    This patch adds a try_import around the import storpool calls
    like we do in other drivers, and it registers the config options
    properly.

    We also move the api setting out of init and into the check_setup
    so the service doesn't crash if somebody tries to load the driver
    without the required storpool modules.

    Closes-Bug: 1405023
    Closes-Bug: 1405022
    Closes-Bug: 1405016
    Closes-Bug: 1403532

    Change-Id: I61340ab7c5abcdc21dbb12cf0693da036e69e90c