Genericize test cases and namespace create pod

This change modifies 020_check-create-pod and 030_check-network test cases to
target `kube-master[0]` instead of `node1` as these tests can be useful in
deployments that do not use the same naming convention as the basic tests.

This change also modifies 020_check-create-pod to namespace into a `test`
namespace allowing the `get pods` command to get its expected number of
running containers.

Closes #866 and #867.

tests/testcases/020_check-create-pod.yml

 ---
-- hosts: node1
+- hosts: kube-master[0]
 
   vars:
     test_image_repo: busybox
@@ -16,11 +16,14 @@
       bin_dir: "/usr/local/bin"
     when: not ansible_os_family in ["CoreOS", "Container Linux by CoreOS"]
 
-  - name: Run a replica controller composed of 2 pods
-    shell: "{{bin_dir}}/kubectl run test --image={{test_image_repo}}:{{test_image_tag}} --replicas=2 --command -- tail -f /dev/null"
+  - name: Create test namespace
+    shell: "{{bin_dir}}/kubectl create namespace test"
+
+  - name: Run a replica controller composed of 2 pods in test ns
+    shell: "{{bin_dir}}/kubectl run test --image={{test_image_repo}}:{{test_image_tag}} --namespace test --replicas=2 --command -- tail -f /dev/null"
 
   - name: Pods are running
-    shell: "{{bin_dir}}/kubectl get pods --no-headers -o json"
+    shell: "{{bin_dir}}/kubectl get pods --namespace test --no-headers -o json"
     register: run_pods_log
     until: [ '(run_pods_log.stdout | from_json)["items"] | map(attribute = "status.phase") | join(",") == "Running,Running"' ]
     retries: 18

tests/testcases/030_check-network.yml

 ---
-- hosts: node1
+- hosts: kube-master[0]
 
   tasks: