fix check for nfs-stack existence
diff --git a/build_lxc.sh b/build_lxc.sh
index 63c9e50..9f133fd 100755
--- a/build_lxc.sh
+++ b/build_lxc.sh
@@ -123,7 +123,7 @@
 # Install and run stack.sh
 apt-get update
 apt-get -y --force-yes install git-core vim-nox sudo
-if [ ! -d "~/nfs-stack" ]; then
+if [ ! -d "/opt/nfs-stack" ]; then
     su -c "git clone git://github.com/cloudbuilders/nfs-stack.git ~/nfs-stack" stack
 fi
 nohup su -c "cd ~/nfs-stack && $STACKSH_PARAMS ./stack.sh" stack &> /opt/run.sh.log