Fix incorrect conferenceableCalls update

Fix recalculateConferenceable() to not differentiate Connferenceables by
whether or not they are currently in the active/background, since it has
no bearing on whether or not a Conferenceable is mergeable with another
Conferenceable. This allows us to send less updates to the
InCallServices when swapping calls in IMS.

Bug: 30676004
Change-Id: I6190364e902941e2969cced7a66e52f00be57064
2 files changed