Check_MK Werk 5835: Improve performance of various event console queries.

ID: 5835 Title: Improve performance of various event console queries. Component: Event Console Level: 1 Class: Bug fix Version: 1.6.0i1 Various event console queries took a very long time, e.g. retrieving the event history of a given host. This could even lead to timeout in the GUI. This was a regression in 1.4.0 compared to 1.2.8 and has been fixed.