SystemUI: Merge battery status "Symbol (Android)" and "Symbol Mini (CM)" with "Theme default" function (1/3):

If enabled battery status "Symbol" or "Symbol Mini (CM)" while "Theme default" is enabled,
load the default symbol icons from system/theme.
This makes more sense, than additional battery styles for default "symbol" and "Symbol & Text".

Change-Id: I035e5422db04dd4e7a38910e349113e350a29c6f