Merge "Sip Message Validators (2/2)" am: e36dfadaff am: 4b875ddaf3 am: b4b759d2ca

Original change: https://android-review.googlesource.com/c/platform/packages/services/Telephony/+/1665979

Change-Id: Id44b8687abe8ab128491b0c348120fc200d2a861