staging: lustre: delete striped directory

Add delete striped directory, it includes

1. enable sync log between MDTs, so slave objects will
   be delete by unlink log, which is similar as deleting ost
   object.

2. retrieve layout information of striped directory on MDT,
   then lock all of the slave objects before unlink.

Signed-off-by: wang di <di.wang@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-3531
Reviewed-on: http://review.whamcloud.com/7445


Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>