Declare the icinga check command also on the master

if not, this error is raised during the restart of icinga:
'critical/config: Error: Validation failed for object 'logstash0.internal.softwareheritage.org!logstash_errors' of type 'Service'; Attribute 'check_command': Object 'check_logstash_errors.sh' of type 'CheckCommand' does not exist.'

Related to T3222