Note that this appears to be fixed in the RUT9XX firmware (tested with `RUT9_R_00.07.01.1`). `ntpclient -h x.x.x.x -c 1` performs a single probe and exits (`-g` seems to work as well). Really happy to see this after spending much of the day looking for options; having the ability to wait for an NTP sync resolves a long standing issue I have had with the RUTs.