Checkmk Werk 12081: proxmox_ve_mem_usage: clear default levels

ID: 12081 Title: proxmox_ve_mem_usage: clear default levels Component: Checks & agents Level: 1 Class: Bug fix Version: 2.1.0i1 Default levels for memory usage have shown to be counter productive so this change disables them. There are no changes for already configured rules or the check algorithm itself.