Switch to using android.telecom.Log in Telecom

Sorry.
CP from: https://android-review.googlesource.com/#/c/287332/

Test: Added unit tests for Log Sessions and Events. All other affected
unit tests still pass.
Bug: 26571395
Change-Id: I890d68d935cd554ba89042e99c155757697e1a37
diff --git a/src/com/android/server/telecom/RingbackPlayer.java b/src/com/android/server/telecom/RingbackPlayer.java
index bfaf8a2..47b6dfe 100644
--- a/src/com/android/server/telecom/RingbackPlayer.java
+++ b/src/com/android/server/telecom/RingbackPlayer.java
@@ -17,6 +17,7 @@
 package com.android.server.telecom;
 
 import com.android.internal.util.Preconditions;
+import android.telecom.Log;
 
 /**
  * Plays ringback tones. Ringback is different from other tones because it operates as the current