login: Adapt SessionManagerDBus methods to generated ones part8.

This CL migrates StartArcInstance method signature.

StartArcInstance and StartArcInstanceForLoginScreen are
merged into StartArcInstance.

BUG=chromium:720240
TEST=Ran cros_workon_make chromeos-login --test. Ran try.

Change-Id: Iee7d322a9a0edb48d89953ccd103e9819ac65577
Reviewed-on: https://chromium-review.googlesource.com/525612
Commit-Ready: Yusuke Sato <yusukes@chromium.org>
Tested-by: Hidehiko Abe <hidehiko@chromium.org>
Reviewed-by: Yusuke Sato <yusukes@chromium.org>
Reviewed-by: Dan Erat <derat@chromium.org>
4 files changed