Create Conferences with a call direction set

Instead of always using UNDEFINED, create conferences with the
direction sent for IMS multiparty conference hosts.

This allows the call to be logged with the correct direction in
the call log.

Bug: 153595501
Test: atest TelecomUnitTests
Change-Id: I7621752f4f6fabeb1b17bac44c4e5e2795c7d052