Set QPID_HOST parameter to better support multi-node mode

When deploying OpenStack in a multi-node configuration,
the Qpid clients need the hostname of the potentially
remote Qpid server in order to permit the necessary RPC
communication between components.

Fixes bug #1196521

Change-Id: Iee3c3747cedea9488ec345e78f8eddbc6e850573
devstack: Add paths specific to XenServer Core

 * XenServer Core keeps its Xapi plugins in a different path to XenServer,
   in order to comply with the Filesystem Hierarchy Standard.

 * XenServer Core mounts devices under /dev/xen/blktap-2 in dom0,
   whereas XenServer mounts them under /dev/sm.

Change-Id: I0a66cd03f000f19c8ff63a8ae4231c00fda88380
Merge "Set QPID_HOST parameter to better support multi-node mode"
Merge "devstack: Add paths specific to XenServer Core"
Merge branch 'master' of github.com:openstack-dev/devstack