Ensure payload is distinct from what's passed in

This is because we modify what comes in (with, at the very least,
:result).

lib/github/ldap/instrumentation.rb

@@ -13,6 +13,7 @@ module GitHub
       #
       # Returns the return value of the block.
       def instrument(event, payload = {})
+        payload = (payload || {}).dup
         if instrumentation_service
           instrumentation_service.instrument(event, payload) do |payload|
             payload[:result] = yield(payload) if block_given?