Configure PKI cache dirs

* Configure Cinder, Glance, Keystone, Nova to put cached credentials
  from keystone.auth_token into /var/cache/<service>

It is not obvious to me that having each of these service share a
credentials cache is a good idea.  It does appear to work but this
patch takes the conservative approach of putting each service's cache
in a distinct directory.

More importantly it gets them out of $HOME!

Change-Id: If88088fc287a2f2f4f3e34f6d9be9de3da7ee00d
diff --git a/stack.sh b/stack.sh
index 7272ec0..af8fbf6 100755
--- a/stack.sh
+++ b/stack.sh
@@ -2042,7 +2042,7 @@
 
 if is_service_enabled g-reg; then
     echo_summary "Uploading images"
-    TOKEN=$(keystone  token-get | grep ' id ' | get_field 2)
+    TOKEN=$(keystone token-get | grep ' id ' | get_field 2)
 
     # Option to upload legacy ami-tty, which works with xenserver
     if [[ -n "$UPLOAD_LEGACY_TTY" ]]; then