Change the common proxy cache manage tasks to be stateful

In certain situation the proxy cache manager may be down, misconfigured,
or otherwise not available. To ensure a consistent environment and give
the deployer a better build experience, especially in the case of an
AIO, the proxy cache common task has been changed to test for cache
availability and add/remove the cache files based on that test.

Change-Id: Ibd0186d67a844ec7b79f423adfb8104d13f72ca5
Closes-Bug: #1632826
Signed-off-by: Kevin Carter <kevin.carter@rackspace.com>

playbooks/common-tasks/package-cache-proxy.yml

@@ -13,18 +13,37 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+- name: test proxy URL for connectivity
+  uri:
+    url: "{{ repo_pkg_cache_url }}/acng-report.html"
+    method: "HEAD"
+  register: proxy_check
+  failed_when: false
+
 - name: Drop apt package manager proxy
   copy:
     content: 'Acquire::http { Proxy "{{ repo_pkg_cache_url }}"; };'
     dest: "/etc/apt/apt.conf.d/00apt-cacher-proxy"
   when:
+    - proxy_check.status == 200
+    - ansible_os_family == 'Debian'
+    - repo_pkg_cache_enabled | bool
+
+- name: Remove apt package manager proxy
+  file:
+    dest: "/etc/apt/apt.conf.d/00apt-cacher-proxy"
+    state: "absent"
+  when:
+    - proxy_check.status != 200
     - ansible_os_family == 'Debian'
     - repo_pkg_cache_enabled | bool
 
 - name: Drop yum package manager proxy
   lineinfile:
     line: 'proxy={{ repo_pkg_cache_url }}'
     dest: "/etc/yum.conf"
+    state: "{{ (proxy_check.status == 200) | ternary('present', 'absent') }}"
   when:
     - ansible_os_family == 'RedHat'
     - repo_pkg_cache_enabled | bool
+