Show where files are copied for sudo switch to stack user

The home directory for the 'stack' user defaults to /opt/stack, which is
not obvious to devstack newbies, and can also be overridden by exporting
a value for DEST.  Therefore it's friendlier to be explicit about the
location of this home directory, to which devstack is copied before
being run as the 'stack' user.

Change-Id: Ia1941a5f2f8cf86a06681e85da52b817a855b8ff
diff --git a/stack.sh b/stack.sh
index 03d5632..b39cd73 100755
--- a/stack.sh
+++ b/stack.sh
@@ -200,8 +200,8 @@
     ( umask 226 && echo "$STACK_USER ALL=(ALL) NOPASSWD:ALL" \
         > /etc/sudoers.d/50_stack_sh )
 
-    echo "Copying files to $STACK_USER user"
     STACK_DIR="$DEST/${TOP_DIR##*/}"
+    echo "Copying files to $STACK_DIR"
     cp -r -f -T "$TOP_DIR" "$STACK_DIR"
     safe_chown -R $STACK_USER "$STACK_DIR"
     cd "$STACK_DIR"