In Wendelin we mostly always want to run our zopes with the soft limit
set to the hard limit.

/reviewed-by @jerome, @jm, @rafael, @vpelletier
/reviewed-on nexedi/slapos!1465

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This patch was already added in nexedi/slapos!1451, but
removed (by force push), due to issues discussed in nexedi/slapos!1451 (comment 193296).