Find: Triggering Ctrl+F selects find text when find is active.

When the find in current document widget is visible and the find string
line edit has currently the keyboard focus triggering the Find/Replace-

Task-number: QTCREATORBUG-8131
Change-Id: Ia1639e2cc6156496afc6c8933988ce2a99902c18
Reviewed-by: Eike Ziller <eike.ziller@digia.com>