Switching the page control autoselects first child element (it shouldn't)

Tested build: 0.4.17-dev-768-g8d44ccd

Steps to reproduce:

• Open System properties with Alt+Enter on My Computer
• Hit Shift+Tab to focus keyboard selection on the page/tab controls
• Press Right arrow several times
• Expected: Keyboard switches between pages/tabs
• Observed: Once page is changed, its first child gets focused

This doesn't allow to switch fast between pages, as one have to Shift+Tab each time a different page is selected. Verified with Windows 2003, it does not focus on the first page child.

It's a regression since 0.4.17-dev-515-g6cb1394.