Updated openstack/openstack
Project: openstack-dev/devstack  dd39fc36f7eb4ae3d3281e24cec8f67fdd5c8242

XenAPI: Fix declare definition

Some versions of bash do not initialise a variable with declare -a
therefore with set -u bash can terminate the script.

Be more verbose in declaring the array if it is not set

Change-Id: I6ec2b6e986aeffe539a2ab93432fa7af9e5a4f5d