Update openstack/common/periodic_task

The following commits are in this update:

1771a77 Adjust import order according to PEP8 imports rule
4bfb7a2 Apply six for metaclass
0ea069e Removed calls to locals()
1a2df89 Enable H302 hacking check

Change-Id: I91c4bf2c18db73f02633b47f7fba6f8c932b4c10
Merge "Update openstack/common/periodic_task"