python: Streamline hosts_to_list
This function used error prone style, using local loop variable in the
scope of the function, making cleanup more risky.
Move ls_entry info the loop scope, and use PyList_SetItem(), stealing
the reference to ls_entry, so we need to decrease the reference count
only on errors.
To use PyList_SetItem() we need to allocate the entire list upfront,
which is good idea anyway.
While refactoring, remove some useless and wrong comments.
Signed-off-by: Nir Soffer <nsoffer@redhat.com>