LU-13252 mgs: Handle possible failure from name_create_mdt

LU-13252 mgs: Handle possible failure from name_create_mdt

name_create_mdt may not succeed if memory allocation fails.

Cray-bug-id: LUS-8503
Signed-off-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Change-Id: I692cfd962e39b7f41d21bcfff1d7577a722ab80d
Reviewed-on: https://review.whamcloud.com/37584
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Petros Koutoupis <petros.koutoupis@hpe.com>