Merge "Hook in DTMF Transport." am: 8ebddb1233 am: c7ea5b871c am: 2f8cf21976

Original change: https://android-review.googlesource.com/c/platform/packages/services/Telephony/+/1566584

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I056f5433969917d5f40612b33a3f64acca2ce214