Check_MK Werk 4375: check_sql: Fixed reporting configuration issues to monitoring core

ID: 4375 Title: check_sql: Fixed reporting configuration issues to monitoring core Component: Checks & Agents Level: 1 Class: Bug Fix Version: 1.5.0i1 The plugin was writing it's textual output to stderr in case of errors or configuration problems which is not processed by the core. So the plugin output could be empty.