Command queue will now allocate more space if it runs out up until
specified maximum size. This makes it to both consume less memory in
most cases and behave better on background rendering cases that
exceeded the old maximum size.

Change-Id: I74d20b9bf7e2f028dd946b9348f0235b0e959682
Reviewed-by: Tomi Korpipää <tomi.korpipaa@theqtcompany.com>
Reviewed-by: Miikka Heikkinen <miikka.heikkinen@theqtcompany.com>