intial take on ceph-brag-client and tox. Python 2.7 passes

Signed-off-by: Alfredo Deza <alfredo@deza.pe>
add backport of collections.Counter for python2.6

Using Raymond Hettinger's MIT backport

Signed-off-by: Alfredo Deza <alfredo.deza@inktank.com>
remove unused variables, gets all tox envs passing

Signed-off-by: Alfredo Deza <alfredo.deza@inktank.com>
Merge pull request #1879 from ceph/wip-8321

fix incompatible `Counter` usage on Python 2.6

Reviewed-by: Loic Dachary <loic@dachary.org>