Conference Call at connection

If there is an ongoing conference call at Bluetooth HFP connect make
sure that it gets registered with telecom.

Bug: 35423819
Bug: 67034276
Test: start a conference call then connect Bluetooth.
Change-Id: I8ca42769e16b6cf2b15aa87747ff01fbf5918220
(cherry picked from commit f9badc6f621c4b48bb624aff59b89f6d3a9bda0a)