Revert "Fix conference call cannot be hung up"

This reverts commit f165e4de31f54be05f917975f9908bcb6e5d4a9c.

Reason for revert: caused b/123957741

Bug: 123957741
Test: manual - make conference call and swap
Change-Id: Id6b35654e75e67df1b5ccba909c585d2d58a5afa
1 file changed