Before SERVER-52538, when you add a document validator to a collection with the "collMod" command, the default validationAction/Level are explicitly included in the collection's catalog entry. They appear in listCollections:

> db.runCommand({collMod: "collection", validator: ...})
{ok: 1}
> db.getCollectionInfos()
[
  {
    "name" : "foo",
    "type" : "collection",
    "options" : {
      "validator" : ...,
      "validationLevel" : "strict",
      "validationAction" : "error"
    }
]

Oddly, if you create a collection with a validator using the "create" command, the default validation action/level are OMITTED from the catalog entry. This difference is probably unintentional but we should preserve it.

After SERVER-52538's second commit, I accidentally changed this behavior, and collMod would OMIT validation action/level from the catalog entry if the user didn't pass values for them. concurrency_replication_multiversion and other suites started failing due to the inconsistency between old and new mongods' behavior.

It's possible I introduced an inconsistency between collMod's behavior on primaries and secondaries, but I didn't investigate. Probably not, since we only saw failures in the multiversion suites.

To fix this, I'll restore collMod's quirk: the default validation action/level are explicitly added to the catalog entry even when the user doesn't pass them.