Change value of SECRET_KEY

Currently SECRET_KEY points to
{ install_lib_dir }}/openstack_dashboard/local/.secret_key_store
however this directory is not writable by www-data:www-data and
attempting to load horizon results in a LockFailed exception being
raised.  Rather than making
{ install_lib_dir }}/openstack_dashboard/local/ writable by
www-data:www-data, we create /var/lib/horizon and point SECRET_KEY to
/var/lib/horizon/.secret_key_stone.
Default swift-proxy group for haproxy purposes

This avoids a situation where we can't setup haproxy as swift isn't being used.
Default the swift-proxy group to a string so the key error is avoided.

Fixes: #375
Merge pull request #376 from andymcc/haproxy_swift

Default swift-proxy group for haproxy purposes
Revert "Default swift-proxy group for haproxy purposes"
Merge pull request #377 from rcbops/revert-376-haproxy_swift

Revert "Default swift-proxy group for haproxy purposes"
Merge pull request #366 from mattt416/issue_362

Change value of SECRET_KEY
Added missing comma which caused Kibana dashboard to not load
Merge pull request #389 from jameswthorne/master

Added missing comma which caused Kibana dashboard to not load
Ensure swift-proxy containers aren't created when not using swift.

* Adjust the environment so that swift_proxy isn't part of infra
* Fix md5sum for environment file in rpc_user_config

HAProxy will work without swift-proxy containers as the group exists
in the inventory but is empty. The VIP will be created but has no
backends.

Fixes: #392
Fixes: #393
Merge pull request #399 from andymcc/swift_env_fix

Ensure swift-proxy containers aren't created when not using swift.
Merge pull request #395 from mancdaz/master-373

supply a list of memcache servers rather than the load balancer IP
remove memcache from f5 config generator

Addresses #373