sanlock: fail acquire with IDLIVE more quickly
    
    When attempting to acquire a lease held by another
    host, we check if the owner is alive by seeing its
    delta lease timestamp change, and then return the
    IDLIVE failure.
    
    If the paxos acquire function doesn't immediately see
    a change in the owner's timestamp, it can also check
    if the local renewal thread saw the owner's timestamp
    change the last time it was checked, and if so return
    IDLIVE.  This avoids having to potentially wait and
    watch the delta lease for a number of seconds before
    failing with IDLIVE.
    
    Signed-off-by: David Teigland <teigland@redhat.com>