Correctly source .stackenv

Specifically to recall HOST_IP and SERVICE_HOST for the current DevStack configuration.

Bug 930274

Change-Id: I299d94101ab93faccc88917503409e0afaa0a523
diff --git a/openrc b/openrc
index 3ef44fd..8af2854 100644
--- a/openrc
+++ b/openrc
@@ -27,8 +27,8 @@
 source $RC_DIR/stackrc
 
 # Load the last env variables if available
-if [[ -r $TOP_DIR/.stackenv ]]; then
-    source $TOP_DIR/.stackenv
+if [[ -r $RC_DIR/.stackenv ]]; then
+    source $RC_DIR/.stackenv
 fi
 
 # Get some necessary configuration