Rename heat-kubernetes to kubernetes, heat-mesos to mesos,
docker-swarm to swarm in templates. We use heat templates and
no other methods, so I think it is unnecessary to add heat before
coe. kubernetes, mesos, swarm are better than
heat-kubernetes, heat-mesos, docker-swarm.
Change-Id: I257b35c1c4ef55d3172095736f550f2c55c8d81f
Closes-Bug: #1514682