meta-facebook: watchdog: fix host cycle

There was a issue in power cycle command as poweron was sent
immediately after poweroff where as power status didn't change
so poweron command was ignored. So adding sleep of 6 sec before
sending poweron.

(From meta-facebook rev: 83af1046a8719f6ad44f80a2cce4f8b0dc9565f7)

Change-Id: I8907643578983b8b3851523c780bc59e5528baac
Signed-off-by: Vijay Khemka <vijaykhemka@fb.com>
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>