Checkmk Werk 11895: omd_info: only create host label 'cmk/check_mk_server:yes' if sites are present

ID: 11895 Title: omd_info: only create host label 'cmk/check_mk_server:yes' if sites are present Component: Checks & agents Level: 1 Class: Bug fix Version: 2.1.0i1 Previously, the host label 'cmk/check_mk_server:yes' was set whenever `omd` was in the path. This a bit too general. We now only set the label, if at least one site is present.