Check_MK Werk 3643: Fixed check_mkevents active check.

ID: 3643 Title: Fixed check_mkevents active check. Component: Checks & Agents Level: 1 Class: Bug Fix Version: 1.2.9i1 check_mkevents didn't make sure that the whole request was sent. Furthermore, it didn't shutdown the socket after sending the request. This (or sending an empty line) is necessary in recent versions of mkeventd.