[autotest] bluetooth_device_xmlrpc_server: device_is_connected method

Add an API to query if a device is connected.

BUG=chromium:545808
TEST=not used yet

Change-Id: I866aa0efc9801939a8e7ca635564a6768a97efd0
Reviewed-on: https://chromium-review.googlesource.com/307642
Commit-Ready: Cheng-Yi Chiang <cychiang@chromium.org>
Tested-by: Cheng-Yi Chiang <cychiang@chromium.org>
Reviewed-by: Hsinyu Chao <hychao@chromium.org>
2 files changed