Changes

RAN_Emulation: Allow setting reason in primitive MSC_CONN_PRIM_DISC_REQ

This allows setting a specific reason in the CREF transmitted on the
wire, other than "End user originted (0)".
A follow-up commit will add a test in HNBGW_Tests where an emulated MSC
answers with CREF reason "End user failure (0x02)".

Change-Id: I1fa1148135625d840426b52450bf52da10448471