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

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

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: Ie8bc540f321382165c2d636a5fd98a6a005e66f2