offload deletion to disk IO thread

core/src/main/groovy/com/muwire/core/files/directories/WatchedDirectoryManager.groovy

@@ -149,9 +149,10 @@ class WatchedDirectoryManager {
             log.warning("unshared a directory that wasn't watched? ${e.directory}")
             return
         }
-        
+        diskIO.submit({
-        File persistFile = new File(home, wd.getEncodedName() + ".json")
+            File persistFile = new File(home, wd.getEncodedName() + ".json")
-        persistFile.delete()
+            persistFile.delete()
+        } as Runnable)
     }
     
     private void sync() {