shill: create Sockets object in RTNLHandler

Create and maintain Sockets object in RTNLHandler to prevent the
possibility of Sockets object being destructed before RTNLHandler.

BUG=chromium:448823
TEST=USE="asan clang" FEATURES=test emerge-$BOARD shill apmanager
         Verify we still have network connectivity through shill
         Verify apmanager doesn't seg fault when exiting

Change-Id: I3a60068718ba6c547cef1437aa1fec22bd27e3eb
Reviewed-on: https://chromium-review.googlesource.com/240801
Trybot-Ready: Zeping Qiu <zqiu@chromium.org>
Tested-by: Zeping Qiu <zqiu@chromium.org>
Reviewed-by: Paul Stewart <pstew@chromium.org>
Commit-Queue: Zeping Qiu <zqiu@chromium.org>
2 files changed