remove configuration files when nuking

Reference issue: http://tracker.ceph.com/issues/9975

Example of a successful run:

    2014-11-06 09:50:13,139.139 INFO:teuthology.nuke:removing temporary configuration files on ubuntu@plana07.front.sepia.ceph.com
    2014-11-06 09:50:13,140.140 INFO:teuthology.nuke:removing temporary configuration files on ubuntu@plana48.front.sepia.ceph.com
    2014-11-06 09:50:13,141.141 INFO:teuthology.nuke:removing temporary configuration files on ubuntu@plana41.front.sepia.ceph.com

After nuking them here is one of the servers confirming that file is gone: 

    (virtualenv)alfredo@teuthology:~/code/teuthology$ ssh ubuntu@plana07.front.sepia.ceph.com cat .cephdeploy.conf
    The authenticity of host 'plana07.front.sepia.ceph.com (10.214.131.33)' can't be established.
    ECDSA key fingerprint is 9d:98:79:b4:5a:fd:ec:f4:3d:e0:ea:24:22:0f:10:e7.
    Are you sure you want to continue connecting (yes/no)? yes
    Warning: Permanently added 'plana07.front.sepia.ceph.com,10.214.131.33' (ECDSA) to the list of known hosts.
    cat: .cephdeploy.conf: No such file or directory