Add ZUUL_USER_SSH_PUBLIC_KEY to opensuse-15 image
Add ZUUL_USER_SSH_PUBLIC_KEY to opensuse-15 image

This was forgotten when it was moved to nb04, and zuul can't log in.

Change-Id: Ib37d2969a7fbaafd161cce9cc66e11c64af49895

openstack-infra/project-config,openstack-infra/project-config