Avoid duplication error when ringserver and storage are on the same node

This commit aims to avoid duplication error when the ringserver and the storage node
are on the same machine. For example when using loopback devices.

Change-Id: Ic09af5d3a706d1a59c3fee7689b373d0a4de4e80
(cherry picked from commit f7d1385d6990492705ddaa228ffa544ca235913a)
Add swift::proxy::crossdomain class

Change-Id: Ie7e5dfc3732ad552063293f16aa04a791bc5add8
swift::proxy::crossdomain class is used to configure crossdomain middleware.
(cherry picked from commit 9d592f61e4529795d51c481d0a33c86c84c0b6af)
Merge "Add swift::proxy::crossdomain class" into stable/icehouse