e2e: replace ssh with net=host hostexec pod and kubectl exec

- document needed packages in hostexec image
- add RunHostCmdOrDie
- kube-proxy e2e: port from ssh to hostexec
  - use preset NodeName to schedule test pods to different nodes
  - parallel launch of pods
  - port from ssh to hostexec
  - add timeout because nc might block on udp
  - delete test container without grace period
- PrivilegedPod e2e: port from ssh to hostexec
- NodePort e2e: port from ssh to hostexec
- cluster/mesos/docker: Enable privileged pods

cluster/mesos/docker/docker-compose.yml

@@ -86,6 +86,7 @@ apiserver:
     --service-node-port-range=30000-32767
     --cloud-provider=mesos
     --cloud-config=/opt/mesos-cloud.conf
+    --allow-privileged
     --tls-cert-file=/var/run/kubernetes/auth/apiserver.crt
     --tls-private-key-file=/var/run/kubernetes/auth/apiserver.key
     --runtime-config=experimental/v1alpha1
@@ -138,6 +139,7 @@ scheduler:
     --mesos-user=root
     --api-servers=http://apiserver:8888
     --mesos-master=mesosmaster1:5050
+    --allow-privileged
     --cluster-dns=10.10.10.10
     --cluster-domain=cluster.local
     --mesos-executor-cpus=1.0