Checkmk Werk 11880: ups_capacity: Bring back UPS 'capacity' metric

ID: 11880 Title: ups_capacity: Bring back UPS 'capacity' metric Component: Checks & agents Level: 1 Class: Bug fix Version: 2.1.0i1 In versions 1.6.0p12 to 1.6.0p19 the 'capacity' metric was not produced if the correspinding devices were on main power supply. Note that some devices report "0 minutes left" in case they are on mains. In this case no levels are applied, to avoid false positives.