Add advertise-client-urls to etcd2 launch options.
Add advertise-client-urls to etcd2 launch options.

- As of etcd 2.0.11 (see here: https://github.com/coreos/etcd/releases/tag/v2.0.11)
 the -advertise-client-urls option is mandatory.

tcichowicz/kubernetes-vagrant-coreos-cluster,lrolaz/kubernetes-vagrant-coreos-cluster,v1k0d3n/kubernetes-vagrant-coreos-cluster,geseib/kubernetes-vagrant-coreos-cluster,lrolaz/kubernetes-vagrant-coreos-cluster,pires/kubernetes-vagrant-coreos-cluster,ericjperry/kubernetes-vagrant-coreos-cluster,schatt/kubernetes-vagrant-coreos-cluster,potgieterdl/kubernetes-vagrant-coreos-cluster,BitBldr/kubernetes-vagrant-coreos-cluster,ndobson/kubernetes-vagrant-coreos-cluster,RichardKnop/paas,amannm/kubernetes-vagrant-coreos-cluster,gaia-sandbox/kubernetes-vagrant-coreos-cluster,prashanthrv/kubernetes-vagrant-coreos-cluster