We found a bug recently where either oslo.cache or python-memcached
aren't using the `backend_argument` properly with more than one
memcached server defined. Until we get the memcached client libraries
figured out, `memcache_servers` works just the same for a single
memcached instance and it works defined with a ring of memcached
instances.
The current variable used for the directive memcache_servers was
pointing to localhost servers, that were historically used for
UUID token cache. Only the ``keystone_cache_backend_argument``
has the right list of servers, but the variable's content is
already formatted to match the cache_backend_argument directive,
and therefore needs editing to be used in ``memcache_servers``.
This is far too fragile, and simplification was needed. This
patch moves to a new variable (with a graceful deprecation
cycle), ``keystone_cache_servers``, a simple list containing the
servers.
The variable ``keystone_memcached_max_compare_and_set_retry``
wasn't used and was therefore removed too.
Related-Bug: 1743036
Closes-Bug: 1681695
Co-Authored-By: Lance Bragstad <lbragstad@gmail.com>
Change-Id: I85ebce8b41dd440e1866a08aa1329b3df798c04f
ab66ca247e