Move default Keystone API version to v3

This patch sets Keystone v3 as default in services
configuration files and in the openrc and stackrc scripts.

Change-Id: I24546f02067ea23d088d383b85e3a78d7b43f166
Partially-Implements: bp keystonev3
diff --git a/stackrc b/stackrc
index ea8b044..e4ff1b7 100644
--- a/stackrc
+++ b/stackrc
@@ -158,7 +158,7 @@
 fi
 
 # Configure Identity API version: 2.0, 3
-IDENTITY_API_VERSION=${IDENTITY_API_VERSION:-2.0}
+IDENTITY_API_VERSION=${IDENTITY_API_VERSION:-3}
 
 # 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