Add swift-ring-builder multi region support

Since Swift 1.8.0, there is the region layer of topology above zones.
swift-ring-builder supports this natively and this commit allows a user to
specify a region when creating devices.
We maintain backwards compatibility by defaulting to region '1'.
The coverage of the ring builder spec tests were also improved as part of
this commit.

Change-Id: I67cbe6b87c84778f71df59cf00f2c5175342bc1b