[unpackfs] Needs mount before it

- The mount module must happen before unpackfs because that (mount)
   module sets up the root mount point (in /tmp) and some other
   variables needed later.

src/modules/unpackfs/module.desc

@@ -4,3 +4,5 @@ type:       "job"
 name:       "unpackfs"
 interface:  "python"
 script:     "main.py"
+requiredModules:
+ - mount