LU-4849 lfs: Avoid double closedir() on err from cb_mv_init()

LU-4849 lfs: Avoid double closedir() on err from cb_mv_init()

In cb_mv_init(), set *dirp to NULL if the parent cannot be opened.
This will avoid a double free when closedir() is called a second
time on the way out of llapi_semantic_traverse()

Signed-off-by: Swapnil Pimpale <spimpale@ddn.com>
Change-Id: I115137f01cd4e370f4ef766028ad9269e85ed10a
Reviewed-on: http://review.whamcloud.com/9905
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>