integration: Use vars_files in plays

It's unsightly and hard to maintain collections of references and long
lists across multiple playbooks/include files.  Centralize them all
in ``vars.yml``, then include that in all plays.

Minor: Update all files with a newline at the start and end.

Signed-off-by: Chris Evich <cevich@redhat.com>

contrib/test/integration/build/plugins.yml

@@ -1,4 +1,5 @@
 ---
+
 - name: clone plugins source repo
   git:
     repo: "https://github.com/containernetworking/plugins.git"
@@ -46,4 +47,4 @@
     src: "{{ ansible_env.GOPATH }}/src/github.com/containernetworking/plugins/bin/bridge"
     dest: "/opt/cni/bin/bridge-custom"
     mode: "o=rwx,g=rx,o=rx"
-    remote_src: yes
+    remote_src: yes