Collect physical host facts if missing

Allow the role to collect facts for the physical host if missing,
since the role has a hard dependency on checking the physical host's
kernel version.

In the OSA container create playbook[1], facts are collected only
if the physical host itself is included in the playbook scope. When
a '--limit containername' parameter is used, no physical host facts
are collected and the role fails with:

The conditional check 'hostvars[physical_host]['ansible_kernel'] |
version_compare('3.18.0-0-generic', '<')' failed. The error was:
Version comparison: 'dict object' has no attribute 'ansible_kernel'

Change-Id: Id84aefed6c0129909cb6153258863564c7cc914a

tasks/main.yml

@@ -29,6 +29,14 @@
   tags:
     - always
 
+- name: Collect physical host facts if missing
+  action:
+    module: setup
+  delegate_to: "{{ physical_host }}"
+  delegate_facts: yes
+  when:
+    - hostvars[physical_host]['ansible_kernel'] is not defined
+
 - name: Kernel version and LXC backing store check
   debug:
     msg: "Using overlayfs is not recommended when using Kernel version < 3.18"