Write lock doesn't depend on pending read locks
Write lock doesn't depend on pending read locks

The while loop polling for write lock aquiring only
matters because there can be multiple readers.  Because
there can only be a single writer, we don't need to
account for this when acquiring a write lock, the normal
locking mechanism takes care of this.

Verified the change with the scripts/threadedtest.py script.

jamesls/flask-shelve