Fix two small typos in marconi/queues/storage/sharding.py
Fix two small typos in marconi/queues/storage/sharding.py

Replace 'preferabaly' with 'preferably' and 'fron' with 'from'

Change-Id: I547fc679edd6f2a1077265273d480f957f5994d1

rackerlabs/marconi,openstack/zaqar,openstack/zaqar,openstack/zaqar,openstack/zaqar