Padding expires_in by 5 minutes on dalli key write to facilitate...

Padding expires_in by 5 minutes on dalli key write to facilitate :race_condition_ttl working correctly.

activesupport/lib/active_support/cache/mem_cache_store.rb

@@ -132,6 +132,10 @@ def write_entry(key, entry, options) # :nodoc:
           method = options && options[:unless_exist] ? :add : :set
           value = options[:raw] ? entry.value.to_s : entry
           expires_in = options[:expires_in].to_i
+          if expires_in > 0 && !options[:raw]
+            # Set the memcache expire a few minutes in the future to support race condition ttls on read
+            expires_in += 5.minutes
+          end
           @data.send(method, escape_key(key), value, expires_in, options)
         rescue Dalli::DalliError => e
           logger.error("DalliError (#{e}): #{e.message}") if logger