library/roles/nagios/files/check_openmanage: new version of the check, fixes some bugs.
xen/roles/monitoring/templates/xen-nrpe.cfg.j2: Run the newest version of check_openmanage.
library/roles/nagios: conditionally use users_system_users to allow unprivileged users in the nrpe users check.
library/vars/isti-global.yml: add a second IP for nagios.