Make the battery applet to remain inactive when batteries are in "NoCharge" state

Fix , making the battery inactive when it's not charging. The systray
will make the work to show/hide the applet when necessary and the user can configure
it's behavior through systray's config options.

Bonus points for not adding a new option to the applet's settings ;)

Tested with kdelibs and kdebase-workspace, both master branches.

Patch by: Thiago Jung Bauermann
Signed-off-by: Artur Duque de Souza