BUG #13029. Fix auto-apply.

Due to the order of how the slots were connected, pqProxyWidget ended up getting
changeFinished() signal before changeAvailable() which was causing the reported
bug. This overcomes the issue by ensuring that changeFinished() is always fired
after changeAvailable().

Change-Id: I948e8515ee40105b962ac1a29e4632489b2a18bd
Merge topic '13029_fix_auto_apply' into next

9499c66 BUG #13029. Fix auto-apply.