Check_MK Werk 8577: Fixed Livestatus queries for custom_variable_names columns.

ID: 8577 Title: Fixed Livestatus queries for custom_variable_names columns. Component: The Check_MK Micro Core Level: 1 Class: Bug Fix Version: 1.4.0i3 Previously, Livestatus queries for custom_variable_names columns had to prepend an underscore to a variable name to find a given variable. This was an implementation detail which should not shine through, and it was highly inconsistent with the handling of custom_variables columns. This has been fixed, so no spurious underscore is needed anymore.