Add switch for /etc/hosts file management

OSA does not need to manage /etc/hosts if the operator's environment
has DNS resolvers that handle local resolution of the hosts and
containers in OSA's environment. This change adds an override switch
to disable /etc/hosts file management.

Change-Id: Id5513107078adb437a2e42220b73811c50f6eb12

defaults/main.yml

@@ -20,6 +20,11 @@ openstack_host_sysstat_enabled: true
 openstack_host_sysstat_interval: 1
 openstack_host_sysstat_statistics_hour: 23
 
+## Enable/disable /etc/hosts file management
+## You should make other arrangements for name resolution
+## of OSA containers and hosts if disabling this
+openstack_host_manage_hosts_file: true
+
 ## Defined required kernel. presently 3.13.0-32-generic
 openstack_host_required_kernel: 3.13.0-34-generic
 

tasks/main.yml

@@ -17,6 +17,7 @@
 - include: openstack_host_packages.yml
 - include: openstack_sysstat.yml
 - include: openstack_update_hosts_file.yml
+  when: openstack_host_manage_hosts_file | bool
 - include: openstack_lvm_config.yml
 - include: openstack_kernel_check.yml
 - include: openstack_kernel_modules.yml