LU-11642 mdt: revoke remote LOOKUP lock in dir layout shrink

LU-11642 mdt: revoke remote LOOKUP lock in dir layout shrink

mdt_dir_layout_shrink() should revoke remote LOOKUP lock if parent
is remote, because it will alter dir layout, which is refreshed
upon lookup.

Signed-off-by: Lai Siyao <lai.siyao@whamcloud.com>
Change-Id: I26ae1af5da6142b44005e5d9ea11293af65ed7b5
Reviewed-on: https://review.whamcloud.com/33640
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Hongchao Zhang <hongchao@whamcloud.com>
Reviewed-by: Mike Pershin <mpershin@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>