[Development] Backporting the "stop unloading plugins" change to 5.6

[André Pönitz]

On Wed, Oct 12, 2016 at 09:59:06PM +0200, Thiago Macieira wrote:
> Hello
> 
> We've got a number of issues that got fixed in 5.7 by the change that made 
> QFactoryLoader stop unloading plugins (notably,

Not unloading plugins is not a fix.

Andre'