IMS:3-way Conf Success but Active call refer fails

Scenario:
A calls B,A calls C,B-Hold, C-Active, Merge
Merge success but only B is added to conference
C is on Hold
UI should display both calls.i.e.Conf call & held call
Since we use Call C's session for new conf call,
report held call as phantom call.

Change-Id: Id4b1e3eb16e4597ed768ad24bc81263008daa711
CRs-Fixed: 781247