LU-9325 mds: replace simple_strtol use with target_name2index()

LU-9325 mds: replace simple_strtol use with target_name2index()

With simple_strtol() going away in the future we should move to
kstrtoXXX functions. Looking a the simple_strtol() use in lod and
osp layer that its use is really target_name2index(). We can
migrate to this function so we have one stop to update from using
simple_strtol().

Change-Id: Ia3d0208c1b1c6bfbe9aa03ce3c068d41ed2c7595
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-on: https://review.whamcloud.com/36551
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Shaun Tancheff <stancheff@cray.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Neil Brown <neilb@suse.de>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>