Fix test mode in non-dev builds
Reintrospect config spec when amending the non-dev cached stdlib with
`_testmode` bits.  This fixes prod package build test runs.
@@ -735,6 +735,10 @@ async def _init_stdlib(
stdlib,
)
await conn.execute(testmode_sql)
+ # _testmode includes extra config settings, so make sure
+ # those are picked up.
+ config_spec = config.load_spec_from_schema(stdlib.stdschema)
+ config.set_settings(config_spec)
# Make sure that schema backend_id properties are in sync with
# the database.
