LU-4398 llite: do not cache write open lock for exec file

LU-4398 llite: do not cache write open lock for exec file

This is to avoid the problem that the MDT needs an extra lock
revocation to make the file be able to execute.

Lustre-change: https://review.whamcloud.com/32265
Lustre-commit: 6dd9d57bc006a37731d34409ce43de13c192e0cc

Signed-off-by: Jinshan Xiong <jinshan.xiong@uber.com>
Signed-off-by: Gu Zheng <gzheng@ddn.com>
Change-Id: Ibb42a9a8cb56a9bf48a6e972b72d3d71ed7fbaf5
Reviewed-by: Lai Siyao <lai.siyao@whamcloud.com>
Signed-off-by: Minh Diep <mdiep@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/36680
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>