playbook: increase max open file soft limit of all processes in vifib machines

playbook/roles/vifib-server/files/slapos_limit.conf

@@ -16,3 +16,8 @@ root             hard    nofile          1048576
 # This days VIFIB machines have at least 16GB of RAM so 64M should not be a big expense.
 # Example use-case: wendelin.core 2 tests need to be able to mlock 64M.
 root             hard    memlock         65536
+
+# For machines with many partitions, supervisord spawns a lot of processes and
+# it doesn't increase its own soft limit. So we increase the soft limit for all
+# processes !
+root             soft    nofile          65536