Method readNext

fdbserver/DiskQueue.actor.cpp:997–997

	Future<bool> initializeRecovery(location recoverAt) override { return initializeRecovery(this, recoverAt); }
	Future<Standalone<StringRef>> readNext(int bytes) override { return readNext(this, bytes); }

	// FIXME: getNextReadLocation should ASSERT( initialized ), but the memory storage engine needs
	// to be changed to understand the new intiailizeRecovery protocol.