apmanager: claim interfaces from shill

apmanager requires sole ownership of a device before it can successfully
start a hostapd on that device.

The support for reclaiming interfaces from shill when an instance of
shill is started/restarted is not in yet. It requires support for registering
DBusNameOwnerChanged callback to the dbus_object_proxy_ which is not possible
in the current generated proxy code.

BUG=chromium:435704
TEST=unittests and manual test using apmanager on stumpy router

Change-Id: I7f737d0bf55f31c1e4ed2a7e5ffe04943ea056db
Reviewed-on: https://chromium-review.googlesource.com/232752
Reviewed-by: Paul Stewart <pstew@chromium.org>
Commit-Queue: Peter Qiu <zqiu@chromium.org>
Tested-by: Peter Qiu <zqiu@chromium.org>
12 files changed