Ceph

In a number of places, the Ceph Python bindings use the iteritems method, which in Python 3 gives errors like:

g1:/var/log/ceph # ceph balancer status
Error EIO: Module 'balancer' has experienced an error and cannot handle commands: 'dict' object has no attribute 'iteritems' 

In order to make the code compatible with Python 3, these instances of iteritems need to be changed to items, subject to the caveat that, in Python 2, items does not produce an iterator. If the code demands an iterator, the iteritems function from six could be used since ceph-mgr already brings in six as a dependency (indirectly via bcrypt).

Backporting note: include https://github.com/ceph/ceph/commit/5f892430462 in the backport