Revert "Use LXC v2.0.6 on CentOS"

It didn't work, and https://review.openstack.org/473879
should resolve the issue.

This reverts commit 5b171d9800.

Change-Id: Ic8fcc53b5847d7e62d76ec0e4248d3847b861cf9

releasenotes/notes/rhel-lxc-208-issue-3ea3ddf7c28c8e08.yaml

@@ -1,6 +0,0 @@
----
-issues:
-  - |
-    Due to https://bugs.launchpad.net/openstack-ansible/+bug/1697531
-    the version of LXC used for CentOS/RHEL has been temporarily set
-    to v2.0.6.

vars/redhat-7.yml

@@ -27,10 +27,7 @@ lxc_hosts_distro_packages:
   - libseccomp
   - libselinux
   - libselinux-devel
-  ## TODO(odyssey4me):
-  # Remove the version once the solution for the following bug is found.
-  # https://bugs.launchpad.net/openstack-ansible/+bug/1697531
-  - lxc-2.0.6
+  - lxc
   - lxc-devel
   - lxc-libs
   - lxc-templates