Misc fixes for cloud_libvirt and rcontrol

*    rcontrol_paramiko: epoll is in `select`, not `socket`
*    versioning: always use git describe --long for versions
*    cloud_libvirt: clean up error handling and string formatting
*    cloud_libvirt: nicer error message when 'cloud.profile' is not set
*    poni: PEP8 whitespace fixes