Clean up send AddrRegInform packet path

AddressTracker is effectively a model class, so to separate concerns
properly, it should not contain any controller functionality.

This CL deletes sendRegisterAddress() out of AddressTracker in favor of
a getter / Dhcp6AddrRegInformPacket builder function which returns the
packet and updates the retransmission parameters (mIsScheduled and
mEventTime).

Test: TH
Flag: EXEMPT mainline
Change-Id: I6ce18bae81618db6c6c08d6d012097ba2ca592bb
1 file changed