In https://review.openstack.org/363077 the var name was incorrectly
set to keystone_developer_distro_packages instead of
keystone_developer_mode_distro_packages as has been the pattern
used across all the other roles. This patch corrects the var name
to ensure that it fits the same pattern as all other roles.
Change-Id: Ia2d3b14b6d3fcf86bdc53a901f1ef2aa6e8128bd
30bd479510