create a configuration removal function in nuke.py

Signed-off-by: Alfredo Deza <alfredo.deza@inktank.com>
call the new helper in nuke_helper

Signed-off-by: Alfredo Deza <alfredo.deza@inktank.com>
use ctx instead of remotes

Signed-off-by: Alfredo Deza <alfredo.deza@inktank.com>
Merge pull request #353 from ceph/wip-9975

remove configuration files when nuking