Clear out the keystone pki data for each run

This prevents old invalid tokens from working after a rerun of stack.sh
and potentially providing users and tenants that don't exist.

Fixes bug 1089700

Change-Id: Icfc22978e41e459d51b50bc7ad2e6d98d766e402
diff --git a/lib/cinder b/lib/cinder
index 16cbaf3..0ab3fd4 100644
--- a/lib/cinder
+++ b/lib/cinder
@@ -212,6 +212,7 @@
     # Create cache dir
     sudo mkdir -p $CINDER_AUTH_CACHE_DIR
     sudo chown `whoami` $CINDER_AUTH_CACHE_DIR
+    rm -f $CINDER_AUTH_CACHE_DIR/*
 }
 
 # install_cinder() - Collect source and prepare