apmanager: add support for HT capability

Parse wiphy's HT capability and add it to the AP service's configuration
file to correctly support AP in 80211n mode.

BUG=chromium:431763
TEST=unittests and manual test by using python to invoke dbus calls
     to start AP service in 802.11n mode.

Change-Id: I6c902136832eea6b38b806f733231d6cbe14e3f6
Reviewed-on: https://chromium-review.googlesource.com/231681
Reviewed-by: Peter Qiu <zqiu@chromium.org>
Commit-Queue: Peter Qiu <zqiu@chromium.org>
Tested-by: Peter Qiu <zqiu@chromium.org>
11 files changed