Cope with ssh transfer delays over 2 minutes or with system clock changes.

Any of these changes would causes excessive ssh delays. In particular
if a transfer took more than 2 minutes elapsed after the previous
transfer the calculated delay would end up being negative which was
then cast to an unsigned making a delay of around 2 billion milliseconds.

Fix the delay by ensuring that the new delay is relative to the current
time and also aligned with the same seconds offset into a whole minute
as was originally present.
Attempt 2nd and subsequent transfer configuration if 1st config fails.

Do not stop if the first of multiple configured transfers fails.
Stop hiwind gust getting propagated forward to the next reading.

Observed behaviour on WH1080 devices is that the hiwind only
ever gets higher and never drops until the stations daemon is
restarted. With the fix the high reading follows the general
changes in wind speed recording the maximum speed in each
sample period
Merge branch 'ssh-hang-fix' into combined
Merge branch 'ssh-multi-continue' into combined