play end call tone when ring is silent

When the user sets the "Ring and Notifications" volume to 0 and
ends an ongoing call, they should now hear the End-Call tone.

Bug: 200599367
Test: atest com.android.server.telecom.tests.InCallTonePlayerTest
                             #testEndCallTonePlaysWhenRingIsSilent
      + manual testing
Change-Id: Iec001a800a02c6e2b78c9a75219453e34eb74921