Speed up checks to see if instance is ready

[oliverlloyd]

Don't wait for instance checks, check for ssh access and use this to decide ready state.

    # E.g.
    for host in ${hosts[@]} ; do
      if [ ! "$(ssh -q \
        -o StrictHostKeyChecking=no \
        -o "BatchMode=yes" \
        -o "ConnectTimeout=15" \
        -i "$PEM_PATH/$PEM_FILE" \
        -p $REMOTE_PORT \
        $USER@$host echo up)" == "up" ] ; then
        echo "Host $host is not responding"
      fi
    done

[oliverlloyd]

Tried this but it's not really viable to depend on purely having an ssh connection. The extra delay waiting for the instance status checks is probably worth the assurance that the test will run okay.