* for availability check - handle HttError happens during slice extraction (reading of parent stream),
updated reason messages,
moved check availability call under common try/except which handles errors during usual stream read,
moved log messages which indicate start of the stream sync before availability check in to make to understand which stream is the source of errors
* why do we return here and not try next stream?
* fixed bug in CheckStream, now we try to check availability for all streams
c44c3eae48