Fix disco identity comparison function
Fix disco identity comparison function

Callbacks for g_ptr_array_sort() take pointers to the elements, not the
elements themselves. This has tripped me up on several occasions.

Ziemin/telepathy-gabble,Ziemin/telepathy-gabble,Ziemin/telepathy-gabble,Ziemin/telepathy-gabble,jku/telepathy-gabble,mlundblad/telepathy-gabble,jku/telepathy-gabble,jku/telepathy-gabble,mlundblad/telepathy-gabble,mlundblad/telepathy-gabble