Do not call setActive(true) when request input panel to show

Observed in kdevelop, that isEnabled() could be false when switching
between different tabs with Ctrl+Tab. But Qt may still call show()
if you click on the texteditor widget. This leads to isEnabled == false but
setActive(true) is called. This causes kdevelop in a usable state because
keyboard grab will be created and no key event will reach application
because isEnabled == false. Under normal circumstances, key will reach
widget first and triggers another text_input_v2 enable to make input
method work properly.