adapter: Check whether adapter is pending powered

adapter: Check whether adapter is pending powered

The powered setting of adapter is frequently being checked, but the
check only accounts for whether it currently is powered. When powering
off the adapter, there is a brief moment when the adapter is already
off kernel-wise, but powered property is still true.

If powered property is accessed at this time, some problems might
occur. For example, if RemoveDevice DBus API is called, we would still
carry out the request and remove the device from the user space, but
we would fail to remove it from the kernel, therefore resulting an
error when we want to re-pair the device.

This patch addresses this issue by also checking whether adapter is
being powered off when checking for powered.

Reviewed-by: Sonny Sasaka <sonnysasaka@chromium.org>
Signed-off-by: Anuj Jain <anuj01.jain@samsung.com>
Signed-off-by: Ayush Garg <ayush.garg@samsung.com>