itest: reconnect nodes more quickly on SCB restore
itest: reconnect nodes more quickly on SCB restore

Since there is a lot of connecting and disconnecting between nodes in
the channel backup tests, we try to speed up that process by lowering
the min backoff from 1 second to 50 milliseconds. We also make sure we
never wait more than 1 second if it does take multple attempts. This
should sum up and hopefully speed up our tests a bit.

aakselrod/lnd,aakselrod/lnd