Refactor the InetSocketAddress in MulticastPacketReader to use port zero

Refactor the InetSocketAddress in MulticastPacketReader to use port zero
because this value is only a placeholder that will be overwritten
when recvfrom() is called.

Test: atest CtsNetTestCases FrameworksNetTests
Bug: 279691736
Change-Id: Idb9d8a96e1f10eb2ede972125430c84af6b539d9
2 files changed