wdmd: pet after reopen and use 1 sec interval after failure
    
    We need to do a keepalive ioctl after reopening the device.
    
    Also, delaying the final check until the last second can
    sometimes not leave enough time to reactivate the
    watchdog, so check every second after a test failure.
    
    Signed-off-by: David Teigland <teigland@redhat.com>