Makefile: Use latest etcd (in three places) for tests
Makefile: Use latest etcd (in three places) for tests

Use a single version, and the latest so we can spot problems with etcd
updates.

caseydavenport/calico-containers,projectcalico/calico-docker,projectcalico/calico-containers,caseydavenport/calico-docker,projectcalico/calico-containers,insequent/calico-docker,Metaswitch/calico-docker,Metaswitch/calico-docker,caseydavenport/calico-docker,projectcalico/calico-docker,insequent/calico-docker,caseydavenport/calico-containers,projectcalico/calico-containers,caseydavenport/calico-containers