Panel control: Remove a "redraw" redundant.

[jorix]

The patch removes the "redraw" and change the test to show that only happens a "redraw"

The "redraw" occurs by control.events.on in "activate" and "deactivate", the explicit "redraw" is unnecessarily.

Note: In #2752 also proposed to prevent "redraw" but required to add code, not remove it, as here.

Test ok in: FF36, IE8, Chrome6 & Safari5.

[ahocevar]

r10734