debian package + ceph-deploy minor fixes

* the debian packages need python-setuptools as a build dependency
* Add python-pushy to the list of packages required to run ceph-deploy when installed on debian
* The list of path added by ceph-deploy does not cover all the deployment scenarios. In particular, when installed from a package it will end up in /usr/lib/python2.7/dist-packages/ceph_deploy . The error message is removed : the from will fail if it does not find the module.
* add missing python-setuptools runtime dependency to debian/control

Signed-off-by: Loic Dachary <loic@dachary.org>