Add gerritbot for openstack-glance channel

This commit adds openstack-glance to the list of channels for
gerritbot. This commit initially just has it tracking the glance and
python-glanceclient repos.

Change-Id: I6f25ca8fd34b2d89ff3c0d119b307143b3b54c8d
Merge "Add gerritbot for openstack-glance channel"