LU-11051 obd: remove obd_{get,put}ref()

LU-11051 obd: remove obd_{get,put}ref()

obd_getref() and obd_putref() are only used in the lov layer and only
implemented by the lov layer. So they can be removed in favor of
direct calls. Rename lov_{get,put}ref() to lov_tgts_{get,put}ref()
since they do not manage references on the lov device but on its
targets array.

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Change-Id: I0f48eaf4bb42b81b2155c599f361a17dd7bb1ae3
Reviewed-on: https://review.whamcloud.com/32529
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>