[Nut-upsuser] Data stale error after short while

[hyouko at gmail.com]

Hello there.
I looked quickly at the logs:
1. this UPS seems to have a somewhat strange implementation of the
megatec protocol (or maybe it's just the usb-to-serial thing): 'F'
reply begins with '!' - it should be a '#' -, is it always like that?
2. after some time the expected first character ('(') of the 'Q1'
reply is replaced by a '$' but, alas, there was a bug in early
versions of nutdrv_qx that prevented the driver from getting a fresh
reply from the UPS under some circumstances, so probably it gets stuck
using always the same malformed reply.
If possible, upgrade to the current git head, maybe after some replies
with the first character swapped the UPS get back to the usual
behaviour.