Bluetooth: Cancel sync command before suspend and power off

Some of the sync commands might take a long time to complete, e.g.
LE Create Connection when the peer device isn't responding might take
20 seconds before it times out. If suspend command is issued during
this time, it will need to wait for completion since both commands are
using the same sync lock.

This patch cancel any running sync commands before attempting to
suspend or adapter power off.

Signed-off-by: Archie Pusaka <apusaka@chromium.org>
Reviewed-by: Ying Hsu <yinghsu@chromium.org>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>