Include CC addresses when processing MMS group messages

Fix includes PduHeaders.CC addresses when processing
MMS group messages. Previously it was only including
PduHeaders.TO addresses which resulted in receiving
a non-group MMS when sent from an HTC device. Fix
was tested against a HTC Rezound.

--- currently in review in AOSP https://android-review.googlesource.com/#/c/52281/

Change-Id: Iba7a08a047d4dba2791d59940ba4ac307817e397