Fix DatagramSocketTest#test_getRemoteSocketAddress

- The test fails due to recent kernel patch
https://source.codeaurora.org/quic/la/kernel/msm-4.4/commit/net/ipv6?h=rel/msm-4.4&id=23287661af3e2fd5a6a5a7bbe2b8f066203456e0
- getLocalHost() returns IPv4-mapped IPv6 address. The socket connects
from this source address to a IPv6 address, i.e. loopback address. This
is no longer allowed after the kernel patch.
- The purpose is to test connection from IPv6 to IPv6. Change source
address to IPv6 loopback address

Test: DatagramSocketTest#test_getRemoteSocketAddress Pass
with Nexus 6P linux kernel 3.10 with local patch

Bug: 64284671
Bug: 64438334
Bug: 64308860
Bug: 64325565

Change-Id: I0c82567b98e7b87454d603e39ffb9f6592e7fb61
(cherry picked from commit 9a8e89ad)
(cherry picked from commit c49ea680)