Disable multiattach in fullstack tests

[hongbin]

Cinder has disabled 'multiattach' [1], which broke the fullstack test in Fuxi. We need to update the test to disable 'multiattach' as well.

[1] https://review.openstack.org/#/c/428365/

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/440192
Committed: https://git.openstack.org/cgit/openstack/fuxi/commit/?id=d2c8d84b6da8bc2d83564661fd422103212090aa
Submitter: Jenkins
Branch: master

commit d2c8d84b6da8bc2d83564661fd422103212090aa
Author: ricolin <email address hidden>
Date: Thu Mar 2 16:18:41 2017 +0800

    Update test requirement

    Since pbr already landed and the old version of hacking seems not
    work very well with pbr>=2, we should update it to match global
    requirement.

    In addition, this patch disable multiattach in fullstack tests
    since this option was disabled in Cinder [1]

    NOTE: This commit actually contains two fixes: one is for fixing
    the test requirement and the other is for fixing the fullstack
    tests. Ideally, we should split it into two commits but we are not
    able to do it because we need both fixes in one patch to unblock
    the gate.

    [1] https://review.openstack.org/#/c/428365/

    Closes-Bug: #1669494
    Partial-Bug: #1668848
    Change-Id: I6770eda1cf232aa8528190c82f1868a82372b159