Deprecate cinder.cross_az_attach option
Deprecate cinder.cross_az_attach option

Introduced in 1504cbc5d4a27695fa663f0b0f3f7b48745bdb45 in Grizzly, the
use cases around this option are unclear but there have been several
bugs related to it.

For example, 6060888b58db42eea826939852838f9e1c204d2c changed boot from
volume to pass the server instance availability zone to cinder when
creating the volume.  However, if that same AZ does not exist in Cinder,
the volume create request will fail - which is bug 1496235.

Cinder works around this with b85d2812a8256ff82934d150dbc4909e041d8b31
using a config option to allow falling back to a default Cinder AZ if
the one requested does not exist.  By default this fallback is disabled
though.

It also sounds like availability zones in Cinder were an artifact from
when Cinder was split out from the nova-volume service, but Cinder AZ
use cases are also unclear.  And it's also unclear what the relationship
is between AZs in Nova and Cinder.

So given the problems here and the lack of a clear use case to justify
having this configuration option in tree, along with it's added
complexity, deprecate the option for removal.

Related-Bug: #1496235
Related-Bug: #1380780
Related-Bug: #1489575
Related-Bug: #1497253

Change-Id: I52cd3d8867d3b35f5caba377302bfc52c112f1d6

klmitch/nova,klmitch/nova,mahak/nova,cloudbase/nova,zhimin711/nova,bigswitch/nova,gooddata/openstack-nova,rajalokan/nova,NeCTAR-RC/nova,mikalstill/nova,cyx1231st/nova,hanlind/nova,jianghuaw/nova,openstack/nova,BeyondTheClouds/nova,rajalokan/nova,sebrandon1/nova,hanlind/nova,jianghuaw/nova,noironetworks/nova,sebrandon1/nova,devendermishrajio/nova,raildo/nova,phenoxim/nova,Juniper/nova,openstack/nova,mahak/nova,mikalstill/nova,CEG-FYP-OpenStack/scheduler,Juniper/nova,vmturbo/nova,vmturbo/nova,fnordahl/nova,TwinkleChawla/nova,rahulunair/nova,noironetworks/nova,cernops/nova,rajalokan/nova,BeyondTheClouds/nova,gooddata/openstack-nova,gooddata/openstack-nova,rajalokan/nova,devendermishrajio/nova,BeyondTheClouds/nova,cernops/nova,fnordahl/nova,alaski/nova,zhimin711/nova,raildo/nova,cyx1231st/nova,mahak/nova,alaski/nova,rahulunair/nova,klmitch/nova,jianghuaw/nova,cloudbase/nova,sebrandon1/nova,gooddata/openstack-nova,dims/nova,apporc/nova,Juniper/nova,NeCTAR-RC/nova,jianghuaw/nova,CEG-FYP-OpenStack/scheduler,dims/nova,phenoxim/nova,klmitch/nova,TwinkleChawla/nova,vmturbo/nova,rahulunair/nova,mikalstill/nova,openstack/nova,hanlind/nova,cloudbase/nova,cernops/nova,bigswitch/nova,apporc/nova,vmturbo/nova,Juniper/nova