IoBridge.recvfrom: fill in the srcAddr for connected sockets

Ensure that recvfrom() always sets the srcAddress on the DatagramPacket,
not just when isConnected == false.

recvfrom() is currently not widely used and it needs to work in a
different way to support the rewrite of PlainDatagramSocketImpl. The
change will not substantially affect the one existing use case,
Inet6AddressImpl, because it always passes "false" for isConnected.


Test: CtsLibcoreTestCases
Bug: 28609551
Change-Id: Iabb5a258a55578d13fedd299f060c52c5485f9b7