LU-4083 mdt: Take lov_mutex in mdt_reint_unlink and _rename

LU-4083 mdt: Take lov_mutex in mdt_reint_unlink and _rename

Take the mot_lov_mutex lock around mdo_unlink and mdo_rename
to synchronize around striping.

Test-Parameters: testlist=racer
Signed-off-by: James Nunez <james.a.nunez@intel.com>
Change-Id: Iaa00b81fd7cfb25ce5f3dcea3c2d6289d133134f
Reviewed-on: http://review.whamcloud.com/7919
Tested-by: Jenkins
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>