Updated openstack/openstack
Project: openstack/oslo-incubator  50fb4a2279e3d6833b3ecf5b93476e6bd598bdc9

Use MultiStrOpt for policy_dirs

We want to ensure that the values specified for directory names are
treated as strings, so use MultiStrOpt instead of the more general
ListOpt.

Change-Id: I46ab5d768b434133f681d9348ecb4c271d633c21