Checkmk Werk 7935: Fixed execution_time column for passive checks.

ID: 7935 Title: Fixed execution_time column for passive checks. Component: Core & setup Level: 1 Class: Bug fix Version: 1.7.0i1 The execution_time column for passive checks doesn't really make sense, so we set it to a (near) zero value when using the CMC. This is in line with Nagios' behavior.