Fix another space-in-path issue in vagrant provisioner

Author: nathansamson

contrib/vagrant/provision-controller.sh

@@ -52,7 +52,7 @@ knife data bag create deis-apps 2>/dev/null
 
 # Boot the deis-controller VM
 echo_color "Booting $node_name with 'vagrant up'"
-pushd $THIS_DIR/../../
+pushd "$THIS_DIR/../../"
 vagrant up --provision
 if [ $? -gt 0 ]; then
   echo_color "Canceling provision because 'vagrant up' failed"