Cleanup keystone library

IDENTITY_API_VERSION is hardcoded to 3 in most locations already, drop
the remaining occurrences, but keep the variable definition since some
plugins still depend on it. Drop ENABLE_IDENTITY_V2 which no longer
has any effect.

Amend variable list for bootstrap_keystone().

Signed-off-by: Dr. Jens Harbott <harbott@osism.tech>
Change-Id: I06f476d2105bc6ec2b511fc5effcfcc3973eaf97
diff --git a/lib/keystone b/lib/keystone
index 065ca70..349d257 100644
--- a/lib/keystone
+++ b/lib/keystone
@@ -9,7 +9,6 @@
 # - ``tls`` file
 # - ``DEST``, ``STACK_USER``
 # - ``FILES``
-# - ``IDENTITY_API_VERSION``
 # - ``BASE_SQL_CONN``
 # - ``SERVICE_HOST``, ``SERVICE_PROTOCOL``
 # - ``S3_SERVICE_PORT`` (template backend only)
@@ -540,7 +539,7 @@
     # unencryted traffic at this point.
     # If running in Apache, use the path rather than port.
 
-    local service_uri=$auth_protocol://$KEYSTONE_SERVICE_HOST/identity/v$IDENTITY_API_VERSION/
+    local service_uri=$auth_protocol://$KEYSTONE_SERVICE_HOST/identity/v3/
 
     if ! wait_for_service $SERVICE_TIMEOUT $service_uri; then
         die $LINENO "keystone did not start"
@@ -569,7 +568,6 @@
 # This function uses the following GLOBAL variables:
 # - ``KEYSTONE_BIN_DIR``
 # - ``ADMIN_PASSWORD``
-# - ``IDENTITY_API_VERSION``
 # - ``REGION_NAME``
 # - ``KEYSTONE_SERVICE_URI``
 function bootstrap_keystone {