Pure drivers should be reporting multiattach=True

[Patrick East]

Pure backends in Cinder end up with multiattach=False due to the default behavior. This is incorrect as volumes on the Pure array are always multiattach 'enabled' even if not specified for the Cinder volume.

As-is this causes some confusion. The easiest fix is to just report multiattach=True in get_volume_stats

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/221439

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/221439
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=327df72aec6f9b03f513e74e0a22bb40ce590712
Submitter: Jenkins
Branch: master

commit 327df72aec6f9b03f513e74e0a22bb40ce590712
Author: Patrick East <email address hidden>
Date: Tue Sep 8 11:06:36 2015 -0700

    Correctly report multiattach in Pure drivers

    As-is we end up ‘reporting’ to the scheduler that Pure backends do not
    support multiattach. This is confusing because volumes created on a
    Pure FlashArray will always be capable of doing multiattach even if not
    specified by Cinder.

    This change syncs up the reporting to the scheduler and what is actually
    happening on the array.

    Change-Id: I3a1e519efdd0c27f63b049aa686ff9045c260ab7
    Closes-Bug: #1493478