0 free capacity should be reported by VNX Cinder Driver when the pool is Offline

[Jeegn Chen]

When the storage pool is Offline, no more LUN can be created before the pool get out of the status.
So when a pool is Offline, its free capacity is de facto 0.
Current EMCVnxCliBase._build_pool_stats() does not check the status of the pool when returning free_capacity_gb.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/172254

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/172254
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=a47925b0f936440aad572c53d62cf483e6cac022
Submitter: Jenkins
Branch: master

commit a47925b0f936440aad572c53d62cf483e6cac022
Author: Jeegn Chen <email address hidden>
Date: Thu Apr 2 16:42:08 2015 +0800

    VNX Cinder Driver should report 0 free_capacity_gb in some scenarios

    When the storage pool is Initializing, Offline or Deleting, no more LUNs
    can be created before the pool gets out of the state.
    So when a pool is in the 3 states, its free capacity is de facto 0.

    This patch is to add logic to report 0 free capacity accordingly.

    Change-Id: I4ef56d48e987795a48e6dcb23615e4b2a7580452
    Closes-Bug: #1431233