Make prev. default explicit

Signed-off-by: Benoit Donneaux <benoit@leastauthority.com>

morph/grid/local/Vagrantfile

@@ -31,7 +31,9 @@ Vagrant.configure("2") do |config|
     # dev.  But should you want to:
     #
     # domain.memory = 4096
-    domain.memory = 512
+    #
+    # Meanwhile, 1024 was apparently the default with VirtualBox 
+    domain.memory = 1024
 
     # Using a specific pool may help to manage the disk space
     domain.storage_pool_name = pool_name