The need to pass a pointer to RAN connection in order to find
a transaction limits possible use cases of trans_find_by_sm_rp_mr(),
e.g. when we need to find a transaction, but RAN connection is not
established yet.
Moreover, the pointer to RAN connection was only used to obtain
pointers to gsm_network and vlr_subscr, so we can just
pass them directly.
Change-Id: I093f36d63e671e50e54fc6236e97a777cc6da77b
Vadim Yanitskiy