cellular: Expose DBus method to force a modem into activated state.

BUG=chromium-os:36950
TEST=cellular_ModemControl (--technology=EVDO_1X)

Change-Id: I3c8756e3dbd4c33a61cbbcb561e0238470876f59
Reviewed-on: https://gerrit.chromium.org/gerrit/39509
Reviewed-by: Arman Uguray <armansito@chromium.org>
Reviewed-by: Ben Chan <benchan@chromium.org>
Commit-Ready: Thieu Le <thieule@chromium.org>
Tested-by: Thieu Le <thieule@chromium.org>
5 files changed