[TCPKeepalive] Fill correct TOS and TTL value

Fill correct TOS/TTL value by fetching them from kernel with
getsockopt.

bug: 123967966
Test: -build, flash, boot
      -atest FrameworksNetTests

Change-Id: I75b1be51040b4a381163958b4cddd27dbb22bac1
4 files changed