Fix for wrong arity of callback function for c-ares

A few years ago (since 2007, see this commit - bagder/c-ares@50ba81cd230f9054fa7c45cb4202ce8720c502b3  ) C-Ares changed the arity of a ares_callback function type. We have to change cares_callback function acordingly. 

See rhbz #753372 for further details:

https://bugzilla.redhat.com/753372

Signed-off-by: Peter Lemenkov <lemenkov@gmail.com>