Make backup directory in container cache

The /var/backup is created in all containers, so it should be created
in the container cache.

This also ensures that the bind mount to this directory can be done
when the container is first created.

Change-Id: I0e2922b31fe301002837e82970814fe8cbe6088a

vars/redhat-7.yml

@@ -53,6 +53,7 @@ lxc_cache_map:
     /usr/bin/wget https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm -O /tmp/epel-release-latest-7.noarch.rpm
     /usr/bin/rpm -ivh /tmp/epel-release-latest-7.noarch.rpm || true
     yum clean all
+    mkdir -p /var/backup
 
 lxc_cache_packages:
   - ca-certificates

vars/ubuntu-14.04.yml

@@ -60,6 +60,7 @@ lxc_cache_map:
     chmod 700 /root/.ssh
     userdel --force --remove ubuntu || true
     apt-get clean
+    mkdir -p /var/backup
 
 # This forces any modified configurations to remain, and any unmodified configs to be replaced
 # ref: http://serverfault.com/questions/259226/automatically-keep-current-version-of-config-files-when-apt-get-install

vars/ubuntu-16.04.yml

@@ -64,6 +64,7 @@ lxc_cache_map:
     chmod 700 /root/.ssh
     userdel --force --remove ubuntu || true
     apt-get clean
+    mkdir -p /var/backup
 
 # This forces any modified configurations to remain, and any unmodified configs to be replaced
 # ref: http://serverfault.com/questions/259226/automatically-keep-current-version-of-config-files-when-apt-get-install