1. Remove "throws Exception" from the signature so it can be used
in tests that do not already throw Exception.
2. Update comment to reflect the fact that TCP buffer sizes are
set on default network switch, not on connect.
3. Move into the method a class-level static constant that is
only used in that method.
Test: atest ConnectivityServiceTest
Change-Id: Ic2e4fbedc23065efc20e45ea84996b577a8e94b6
b0e7a02891