LU-10346 utils: use the correct lib path in mount_utils.c

LU-10346 utils: use the correct lib path in mount_utils.c

The backfs_load_module() function of mount_utils.c used an outdated
to link itself against the osd library. This patch fixes it.

Test-Parameters: trivial
Lustre-change: https://review.whamcloud.com/30431
Lustre-commit: 74eb79b0fe4815daa0bebd3293c71f052c5b19d4

Signed-off-by: Quentin Bouget <quentin.bouget@cea.fr>
Change-Id: I90a523b45b5772c05f7520e810eec7eac14b75be
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Nathaniel Clark <nathaniel.l.clark@intel.com>
Signed-off-by: Minh Diep <minh.diep@intel.com>
Reviewed-on: https://review.whamcloud.com/30584
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>