This fixes the sample configuration to contain proper
config groups alongway.
Regenerate sample config with oslo's config generator.
DocImpact: Removes the deprecated memcached_server
option from DEFAULT (now in keystone_authtoken group)
Closes-Bug: #1206650
Closes-Bug: #1260322
Change-Id: I170715bfe6ec7dad9f7317e7bb56cbb68034c4ec