staging: lustre: Fix brace {} are not necessary for single statement blocks

This patch fixed "WARNING: braces {} are not necessary for
single statement blocks" in lustre/lustre/mgc_request.c

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>