util/streaming-buffer: add extra safety check

util/streaming-buffer: add extra safety check

Ticket: 7393

Check if GrowRegionToSize is called with an argument
trying to shrink the region size, and if so do nothing,
ie do not try to shrink, and just return ok.

This way, we avoid a buffer overflow from memeset using an
unsigned having underflowed.

(cherry picked from commit 9a53ec43b13f0039a083950511a18bf6f408e432)