LU-5452 lmv: release request in lmv_revalidate_slaves()

LU-5452 lmv: release request in lmv_revalidate_slaves()

In lmv_revalidate_slaves() ensure that the request returned by
md_intent_lock() is properly released on all paths.

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Change-Id: I35d63b248d0c80261ebc97f43722b0c547eb1aac
Reviewed-on: http://review.whamcloud.com/11326
Tested-by: Jenkins
Reviewed-by: wangdi <di.wang@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>