Check_MK Werk 1564: check_mk_agent.linux: fix situation where async plugin is not executed after crash

ID: 1564 Title: check_mk_agent.linux: fix situation where async plugin is not executed after crash Component: Checks & Agents Level: 1 Class: Bug Fix Version: 1.2.5i7 When executing asynchronous sections or plugins the Check_MK Agent uses <tt>run_cached()</tt> for putting them in the background. This function creates a cachefile with the extension <tt>.new</tt> and removes that suffix when the actual plugin has finished. If due to a server crash the file keeps lying around the the plugin would not be executed anymore. We now remove that file if it is older then twice the cache age <i>and we kill</i> any process that still has open that file. That way we avoid overlapping plugins in case of a real hanger.