dfu_mesh: fix bug where a missed packet would cause ever-expanding hole
dfu_mesh: fix bug where a missed packet would cause ever-expanding hole

mrquincle/nRF51-ble-bcast-mesh,mrquincle/nRF51-ble-bcast-mesh,mrquincle/nRF51-ble-bcast-mesh,mrquincle/nRF51-ble-bcast-mesh