Enable Swift's newer feature of container-sync

Newer version of container-sync feature is introduced in Swift ver. 1.12.0.

The spec:
http://docs.openstack.org/developer/swift/overview_container_sync.html

Before this commit, Devstack does not configure any realm used in
container-sync, therefore this feature does not work.
To test this feature in CI system, moreover to show the sample
configuration of realms, Devstack now edits realms configuration file.

Change-Id: I9f1e3224403e08e725a989162729470357fe90b0
Closes-Bug: 1378646
(cherry picked from commit d03915f9c08ff91c5d39f8cadb064718079bdb4b)