utils.renamer() can raise tracebacks

[John Dickinson]

seen on a quarantined container db:

[user@host /srv/node/d1986/quarantined/containers/ab8891de9884920a8869f48afd9b1fde 116]% sudo swift-container-info ab8891de9884920a8869f48afd9b1fde.db
Traceback (most recent call last):
  File "/opt/ss/bin/swift-container-info", line 47, in <module>
    run_print_info(args, vars(options))
  File "/opt/ss/bin/swift-container-info", line 23, in run_print_info
    print_info('container', *args, **opts)
  File "/opt/ss/lib/python2.7/site-packages/swift/cli/info.py", line 382, in print_info
    info = broker.get_info()
  File "/opt/ss/lib/python2.7/site-packages/swift/container/backend.py", line 499, in get_info
    self._commit_puts_stale_ok()
  File "/opt/ss/lib/python2.7/site-packages/swift/common/db.py", line 636, in _commit_puts_stale_ok
    self._commit_puts()
  File "/opt/ss/lib/python2.7/site-packages/swift/common/db.py", line 619, in _commit_puts
    self.merge_items(item_list)
  File "/opt/ss/lib/python2.7/site-packages/swift/container/backend.py", line 895, in merge_items
    return _really_merge_items(conn)
  File "/opt/ss/lib/python2.7/contextlib.py", line 35, in __exit__
    self.gen.throw(type, value, traceback)
  File "/opt/ss/lib/python2.7/site-packages/swift/common/db.py", line 385, in get
    self.possibly_quarantine(*sys.exc_info())
  File "/opt/ss/lib/python2.7/site-packages/swift/common/db.py", line 350, in possibly_quarantine
    renamer(self.db_dir, quar_path, fsync=False)
  File "/opt/ss/lib/python2.7/site-packages/swift/common/utils.py", line 1240, in renamer
    os.rename(old, new)
OSError: [Errno 16] Device or resource busy

The culprit seems to be the os.rename() call inside of the exception handler in the utils.renamer() method.