LU-17000 coverity: Fix leak under mgc_request.c

LU-17000 coverity: Fix leak under mgc_request.c

This patch fixes resource leak error reported
by coverity run.

CoverityID: 403113 ("Resource leak"): mgc_request.c

Test-Parameters: trivial
Signed-off-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Change-Id: Ie569a18cbacdb48c186d38ccc466ce86eeb1b28f
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/52656
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>