set buildvm-s390x-01 to only 1 job at a time to avoid congestion

roles/koji_builder/templates/kojid.conf

@@ -2,8 +2,13 @@
 ; The number of seconds to sleep between tasks
 ; sleeptime=15
 
+{% if host in groups['buildvm-s390x'] and host in groups['runroot'] %}
+; The maximum number of jobs that kojid will handle at a time
+maxjobs=1
+{% else %}
 ; The maximum number of jobs that kojid will handle at a time
 maxjobs=25
+{% endif %}
 
 ; The minimum amount of free space (in MBs) required for each build root
 ; minspace=8192