exercises/aggregates.sh: Only source openrc once

Only source openrc once, and remove the unnecessary re-sourcing of
"functions" which is done by openrc.

Change-Id: I61c87a0742de274d47753a0b216c56d96344d161
diff --git a/exercises/aggregates.sh b/exercises/aggregates.sh
index 01d548d..808ef76 100755
--- a/exercises/aggregates.sh
+++ b/exercises/aggregates.sh
@@ -31,18 +31,13 @@
 EXERCISE_DIR=$(cd $(dirname "$0") && pwd)
 TOP_DIR=$(cd $EXERCISE_DIR/..; pwd)
 
-# Import common functions
-source $TOP_DIR/functions
-
-# Import configuration
-source $TOP_DIR/openrc
+# Test as the admin user
+# note this imports stackrc/functions, etc
+. $TOP_DIR/openrc admin admin
 
 # Import exercise configuration
 source $TOP_DIR/exerciserc
 
-# Test as the admin user
-. $TOP_DIR/openrc admin admin
-
 # If nova api is not enabled we exit with exitcode 55 so that
 # the exercise is skipped
 is_service_enabled n-api || exit 55