sanlock: base kill sig on last renewal
    
    Tracking progression through the grace time by
    counting one retry per second doesn't work in
    the case were sanlock doesn't run every second
    (e.g. sigstop or delayed scheduling).  This will
    cause sanlock to attempt to use killpath even
    when there's nearly no time left before reset.
    So, the transition to sigkill should depend on
    the current time from the last lease renewal.
    
    Signed-off-by: David Teigland <teigland@redhat.com>