Updated openstack/openstack
Project: openstack/oslo.db  96f610bf728fb5429598f119ce15a382ab1283d4

Use the six provided iterator mix-in

Instead of having a customized next() and __next__() methods
just use the mix-in that six provides and used it to avoid
having to declare our own next() compatability function.

Change-Id: I1a5fc9bd43783577af879476ca46afcc668185f5