Fix circle battery opaqueness for the low battery color

Because of the DST_ATOP Xfermode the color was drawn below the full
gray ring resulting in a washed out red. Fix this by not setting an
Xfermode and drawing the color normally.
This does not affect the non-low color as it cannot get any whiter.

Fixes: CYAN-3282

Change-Id: If1183dcb272e84858371be3765ba758fa2560eeb