shill: fix LazyInstance decls for libchrome r456626

These were changed upstream and DestructorAtExit is no longer the
default in newer versions of libchrome (and is in fact considered
not the one users usually want).

CQ-DEPEND=CL:1185338
BUG=b:37434548
TEST=Trybot.

Change-Id: I24f2d6ace58ba0c8c6b4efa7be31458ed0532731
Reviewed-on: https://chromium-review.googlesource.com/1185340
Commit-Ready: Hidehiko Abe <hidehiko@chromium.org>
Tested-by: Hidehiko Abe <hidehiko@chromium.org>
Reviewed-by: Luis Hector Chavez <lhchavez@chromium.org>
Reviewed-by: Ben Chan <benchan@chromium.org>