Use role defaults for lxc_cache_prep_timeout

In https://review.openstack.org/523525 the default value was
changed for SuSE and CentOS to be higher, but the value was
also overridden using role vars which have a high precedence.

This patch ensures that the value uses the role defaults to
ensure it has the lowest precedence. It also changes the reno
to ensure that the change in default is communicated.

The increased timeout will have no real effect on gating, but
will benefit installations where the mirror is a bit slow.

Change-Id: I41a68313d1841d14001acca591db5c5638e53ffc

defaults/main.yml

@@ -134,8 +134,8 @@ lxc_cache_distro_packages: "{{ _lxc_cache_distro_packages }}"
 # The maximum amount of time (in seconds) to wait until failing the cache
 # preparation process. This is necessary to mitigate the issue that can
 # arise where the cache prep hangs and never fails.
-# The value is specified in seconds, with the default being 10 minutes.
-lxc_cache_prep_timeout: 600
+# The value is specified in seconds, with the default being 20 minutes.
+lxc_cache_prep_timeout: 1200
 
 # Set the servers to download LXC images from
 # NOTE(mhayden): The main images.linuxcontainers.org site will redirect

releasenotes/notes/lxc-cache-prep-timeout-97dc18882f7b1e76.yaml

@@ -4,4 +4,4 @@ features:
     The maximum amount of time to wait until forcibly failing the
     LXC cache preparation process is now configurable using the
     ``lxc_cache_prep_timeout`` variable. The value is specified
-    in seconds, with the default being 10 minutes.
+    in seconds, with the default being 20 minutes.

tasks/lxc_cache_preparation.yml

@@ -108,8 +108,6 @@
 - name: Prepare cached image setup commands
   shell: "chroot {{ lxc_image_cache_path }} /usr/local/bin/cache-prep-commands.sh > /var/log/lxc-cache-prep-commands.log 2>&1"
   changed_when: false
-  # It should only take a couple of minutes to prepare the cache. But if network is slow it might take longer.
-  # Lets be optimistic and set the limit to 10 minutes
   async: "{{ lxc_cache_prep_timeout }}"
   poll: 0
   register: _lxc_cache_prepare_commands

vars/redhat-7.yml

@@ -109,8 +109,3 @@ lxc_container_default_interfaces: |
   ONBOOT=yes
   NM_CONTROLLED=no
   TYPE=Ethernet
-
-# The value is specified in seconds, with the default being 20 minutes. This is
-#  double the amount of time used by default to mitigate issues with slow
-#  mirrors / testing nodes.
-lxc_cache_prep_timeout: 1200

vars/suse-42.yml

@@ -105,8 +105,3 @@ lxc_cached_network_interfaces:
 lxc_container_default_interfaces: |
   STARTMODE=auto
   BOOTPROTO=dhcp
-
-# The value is specified in seconds, with the default being 20 minutes. This is
-#  double the amount of time used by default to mitigate issues with slow
-#  mirrors / testing nodes.
-lxc_cache_prep_timeout: 1200