fencing.py: Adds device option login_eol_lf
This option is used for login method using telnet. By default most of the fence agents
work with username\r\n but on some devices (e.g. HP iLO MP, sanbox2) it is interpreted
as there is empty password.
Needed for bz#512947 (sanbox2) and #508722 (fence_ilo-mp)