Fix nova.availability_zones docstring

Change-Id: I66fe5cd5ab688bd4d3bedcdb79823497c65912e9
sync latest log and lockutils from oslo

Change-Id: I2aa0e63a7e9c3b7bea829fddf42a00d3318c6d6f
Merge "sync latest log and lockutils from oslo"
Merge "Fix nova.availability_zones docstring"