Checkmk Werk 10038: Fix cmk/check_mk_server:yes label related issues

ID: 10038 Title: Fix cmk/check_mk_server:yes label related issues Component: Checks & agents Level: 1 Class: Bug fix Version: 1.7.0i1 This label was detected based on the asynchronously created agent section '<<<omd_status>>>'. Because this section is not immediately available on the first agent contact, this resulted in a label discovery after the second check cycle. Another issue was that the '<<<omd_status>>>' section was produced by non Checkmk servers with older agent versions. This lead to a wrong label discovery. We now use the dedicated '<<<labels>>>' section to create the label which is produced once we find the command 'omd' on a system.