#63 Failure to set hi-res on temp sensor is permanent

[Vadim Tkachenko]

If for some reason DAC fails to set high resolution on
DS1820, the high resolution will be lost until the next
time device departs and arrives back (which may be
anywhere from few days to never, if the network is
stable enough).

Fix: if an attempt to set the high resolution fails,
keep retrying once in a while, gracefully retreating if
those attempts keep failing.