Fix memory leak when connecting clients rejected.

ChangeLog.txt

@@ -4,6 +4,7 @@ Broker:
 - Fix `mosquitto_passwd -b` not updating passwords for existing users
   correctly. Creating a new user with `-b` worked without problem.
   Closes #1664.
+- Fix memory leak when connecting clients rejected.
 
 Client library:
 - Don't treat an unexpected PUBACK, PUBREL, or PUBCOMP as a fatal error.

src/handle_connect.c

@@ -886,5 +886,7 @@ handle_connect_error:
 	if(client_cert) X509_free(client_cert);
 #endif
 	/* We return an error here which means the client is freed later on. */
+	context->clean_start = true;
+	context->session_expiry_interval = 0;
 	return rc;
 }