In preparation for Swift global cluster we need a solution that moves
away from a centralised "memcache" server as a distribution mechanism,
since we can't guarantee that all swift hosts will have access to one
memcache server.
This patch uses ansible variables (which were already being set) as the
distribution mechanism so that the authorized_keys file can be generated
by using the ansible variables set for each host as part of the tasks.
Additionally this moves away from using "shell" commands to generate the
key and adjust the authorized_keys file and instead uses the built in
ansible "authorized_keys" module as well as the built in
"generate_ssh_key" option for the "user" module.
Finally this adds a "swift_recreate_keys" option which can be set to
"True" in order to recreate all the swift keys, and recreate the
authorized_keys file. This was happening on every run and will now not
happen by default, unless the variable is set to "True".
Change-Id: Ic4eb05042244c32050233e1445633d5731f9603b
Partially-Implements: blueprint multi-region-swift
e0c8cfc43c