Revert "Move default Keystone API version to v3"

It seems like the fallout from this was not well sorted.
A lot of things aren't working, and there is still vestigial
v2 bits left behind.

This should have come with a much greater warning and some
spot checking of additional services working with this.

This reverts commit b162a1d58cdecfb32847b59bd341e06c26efb1ed.

Change-Id: Ia792b23119c00089542ba08879dca1c29dc80945
diff --git a/stackrc b/stackrc
index 903da80..58146a4 100644
--- a/stackrc
+++ b/stackrc
@@ -130,7 +130,7 @@
 fi
 
 # Configure Identity API version: 2.0, 3
-IDENTITY_API_VERSION=${IDENTITY_API_VERSION:-3}
+IDENTITY_API_VERSION=${IDENTITY_API_VERSION:-2.0}
 
 # Set the option ENABLE_IDENTITY_V2 to True. It defines whether the DevStack
 # deployment will be deploying the Identity v2 pipelines. If this option is set