MB-42352: allow_del_with_meta_prune_user_data true by default

Pre-6.6 versions are affected by invalid payloads generated by
expirations. Ie, body or user-xattrs in the value.
6.6.0 fixes that. But, users of DelWithMeta may still fail validation
when they want to store pre-6.6 data into a 6.6 node. Eg,
backup/restore and XDCR.

Since MB-36321 DelWithMeta can operate in a "sanitizer" mode that is off
by default. This patch enables it, so any invalid payload will be
sanitized and successfully stored in 6.6.

The feature seems to have already a decent test coverage, introduced in
http://review.couchbase.org/c/kv_engine/+/115904/ first and then
expanded in http://review.couchbase.org/c/kv_engine/+/129191.

Change-Id: I3e436bafd98d4eec9d91f34c5d45be882440d57e
Reviewed-on: http://review.couchbase.org/c/kv_engine/+/139468
Reviewed-by: Dave Rigby <[email protected]>
Tested-by: Build Bot <[email protected]>
Well-Formed: Build Bot <[email protected]>

Author: paolococchi

engines/ep/configuration.json

@@ -1,7 +1,7 @@
 {
     "params": {
         "allow_del_with_meta_prune_user_data" : {
-            "default" : "false",
+            "default" : "true",
             "descr": "Let del_with_meta prune user data provided from the user instead of failing",
             "dynamic" : true,
             "type" : "bool"

tests/testapp/testapp_withmeta.cc

@@ -211,6 +211,17 @@ TEST_P(WithMetaTest, MB36321_DeleteWithMetaRefuseUserXattrs) {
         return;
     }
 
+    {
+        auto& conn = getAdminConnection();
+        conn.selectBucket(bucketName);
+        const auto setParam = BinprotSetParamCommand(
+                cb::mcbp::request::SetParamPayload::Type::Flush,
+                "allow_del_with_meta_prune_user_data",
+                "false");
+        const auto resp = BinprotMutationResponse(conn.execute(setParam));
+        ASSERT_EQ(cb::mcbp::Status::Success, resp.getStatus());
+    }
+
     cb::xattr::Blob blob;
     blob.set("user", R"({"band":"Steel Panther"})");
     auto xattrValue = blob.finalize();