Log when AM gives/removes foreground service delegation

In android U, a new call lifecycle was introduced and specified in
TelecomManger#addCall. Clients MUST post a call-style notification in
order to gain foreground service delegation.

Clients who fail to post a notification will have their media playback
and audio recording suppressed. Its even possible that the application
will be cleaned up if its in the background.

Given the consequences, its important to log when Telecom gives FSD to
debug.

bug: 278310214
Test: manual / BR
Change-Id: I8e86161738d61576ca2e2869fa6086efa7166817