The lxc_container_create role has been updated to build containers to
the same distribution and release as the host machine. The
container_release property defined in environment files used to
generate inventory is no longer required.
I7d2aea8f6548feb381bf2354965f05fa0a9a99b8 removed this property from
half of the environment files. This change removes it from all remaining
files.
Change-Id: I8bff7613639676797159eac75cef0dd091bda7a4
97eb3b3378