Change onClientRead() loop

Instead of recursively calling onClientRead(),
use a do/while loop.  This prevents helps the
callstack for Model/View QtRO objects, where
there can be a lot of small packets.

Change-Id: Iecd8ded2ec43c713bfe2abc6ed6753a31d5c39c6
Reviewed-by: Björn Breitmeyer <bjoern.breitmeyer@kdab.com>